diff --git a/loader/db.go b/loader/db.go
index efc200b3c9..ea9dff035a 100644
--- a/loader/db.go
+++ b/loader/db.go
@@ -152,7 +152,7 @@ func (conn *Conn) executeSQL(ctx *tcontext.Context, queries []string, args ...[]
 func createConn(cfg *config.SubTaskConfig) (*Conn, error) {
 	dbDSN := fmt.Sprintf("%s:%s@tcp(%s:%d)/?charset=utf8mb4&maxAllowedPacket=%d",
 		cfg.To.User, cfg.To.Password, cfg.To.Host, cfg.To.Port, *cfg.To.MaxAllowedPacket)
-	baseConn, err := baseconn.NewBaseConn(dbDSN, &retry.FiniteRetryStrategy{})
+	baseConn, err := baseconn.NewBaseConn(dbDSN, &retry.FiniteRetryStrategy{}, baseconn.DefaultRawDBConfig())
 	if err != nil {
 		return nil, terror.WithScope(terror.DBErrorAdapt(err, terror.ErrDBDriverError), terror.ScopeDownstream)
 	}
diff --git a/pkg/baseconn/conn.go b/pkg/baseconn/conn.go
index e7edaf5231..423031e8a0 100644
--- a/pkg/baseconn/conn.go
+++ b/pkg/baseconn/conn.go
@@ -33,14 +33,30 @@ type BaseConn struct {
 	DSN string
 
 	RetryStrategy retry.Strategy
+
+	RawDBCfg *RawDBConfig
+}
+
+// RawDBConfig contains some low level database config
+type RawDBConfig struct {
+	MaxIdleConns int
+}
+
+// DefaultRawDBConfig returns a default raw database config
+func DefaultRawDBConfig() *RawDBConfig {
+	return &RawDBConfig{
+		MaxIdleConns: 2,
+	}
 }
 
 // NewBaseConn builds BaseConn to connect real DB
-func NewBaseConn(dbDSN string, strategy retry.Strategy) (*BaseConn, error) {
+func NewBaseConn(dbDSN string, strategy retry.Strategy, rawDBCfg *RawDBConfig) (*BaseConn, error) {
 	db, err := sql.Open("mysql", dbDSN)
 	if err != nil {
 		return nil, terror.ErrDBDriverError.Delegate(err)
 	}
+	// set max idle connection limit before any database call
+	db.SetMaxIdleConns(rawDBCfg.MaxIdleConns)
 	err = db.Ping()
 	if err != nil {
 		db.Close()
@@ -49,7 +65,7 @@ func NewBaseConn(dbDSN string, strategy retry.Strategy) (*BaseConn, error) {
 	if strategy == nil {
 		strategy = &retry.FiniteRetryStrategy{}
 	}
-	return &BaseConn{db, dbDSN, strategy}, nil
+	return &BaseConn{db, dbDSN, strategy, rawDBCfg}, nil
 }
 
 // SetRetryStrategy set retry strategy for baseConn
@@ -70,6 +86,8 @@ func (conn *BaseConn) ResetConn(tctx *tcontext.Context) error {
 	if err != nil {
 		return terror.ErrDBDriverError.Delegate(err)
 	}
+	// set max idle connection limit before any database call
+	db.SetMaxIdleConns(conn.RawDBCfg.MaxIdleConns)
 	err = db.Ping()
 	if err != nil {
 		db.Close()
diff --git a/pkg/baseconn/conn_test.go b/pkg/baseconn/conn_test.go
index cdfdafa347..4863f592e8 100644
--- a/pkg/baseconn/conn_test.go
+++ b/pkg/baseconn/conn_test.go
@@ -35,7 +35,7 @@ type testBaseConnSuite struct {
 }
 
 func (t *testBaseConnSuite) TestBaseConn(c *C) {
-	baseConn, err := NewBaseConn("error dsn", nil)
+	baseConn, err := NewBaseConn("error dsn", nil, DefaultRawDBConfig())
 	c.Assert(terror.ErrDBDriverError.Equal(err), IsTrue)
 
 	tctx := tcontext.Background()
@@ -53,7 +53,7 @@ func (t *testBaseConnSuite) TestBaseConn(c *C) {
 
 	db, mock, err := sqlmock.New()
 	c.Assert(err, IsNil)
-	baseConn = &BaseConn{db, "", nil}
+	baseConn = &BaseConn{db, "", nil, DefaultRawDBConfig()}
 
 	err = baseConn.SetRetryStrategy(&retry.FiniteRetryStrategy{})
 	c.Assert(err, IsNil)
diff --git a/syncer/checkpoint_test.go b/syncer/checkpoint_test.go
index 2b345dbf2f..3463968706 100644
--- a/syncer/checkpoint_test.go
+++ b/syncer/checkpoint_test.go
@@ -91,7 +91,7 @@ func (s *testCheckpointSuite) TestCheckPoint(c *C) {
 	mock.ExpectCommit()
 
 	// pass sqlmock baseConn directly
-	conn := &Conn{cfg: s.cfg, baseConn: &baseconn.BaseConn{db, "", &retry.FiniteRetryStrategy{}}}
+	conn := &Conn{cfg: s.cfg, baseConn: &baseconn.BaseConn{db, "", &retry.FiniteRetryStrategy{}, baseconn.DefaultRawDBConfig()}}
 	err = cp.Init(conn)
 	c.Assert(err, IsNil)
 	cp.Clear()
diff --git a/syncer/db.go b/syncer/db.go
index 98c793fea0..6e2114080c 100644
--- a/syncer/db.go
+++ b/syncer/db.go
@@ -200,10 +200,10 @@ func (conn *Conn) executeSQL(tctx *tcontext.Context, queries []string, args ...[
 	return conn.executeSQLWithIgnore(tctx, nil, queries, args...)
 }
 
-func createBaseConn(dbCfg config.DBConfig, timeout string) (*baseconn.BaseConn, error) {
+func createBaseConn(dbCfg config.DBConfig, timeout string, rawDBCfg *baseconn.RawDBConfig) (*baseconn.BaseConn, error) {
 	dbDSN := fmt.Sprintf("%s:%s@tcp(%s:%d)/?charset=utf8mb4&interpolateParams=true&readTimeout=%s&maxAllowedPacket=%d",
 		dbCfg.User, dbCfg.Password, dbCfg.Host, dbCfg.Port, timeout, *dbCfg.MaxAllowedPacket)
-	baseConn, err := baseconn.NewBaseConn(dbDSN, &retry.FiniteRetryStrategy{})
+	baseConn, err := baseconn.NewBaseConn(dbDSN, &retry.FiniteRetryStrategy{}, rawDBCfg)
 	if err != nil {
 		return nil, terror.DBErrorAdapt(err, terror.ErrDBDriverError)
 	}
@@ -211,7 +211,7 @@ func createBaseConn(dbCfg config.DBConfig, timeout string) (*baseconn.BaseConn,
 }
 
 func createConn(cfg *config.SubTaskConfig, dbCfg config.DBConfig, timeout string) (*Conn, error) {
-	baseConn, err := createBaseConn(dbCfg, timeout)
+	baseConn, err := createBaseConn(dbCfg, timeout, baseconn.DefaultRawDBConfig())
 	if err != nil {
 		return nil, err
 	}
@@ -221,14 +221,17 @@ func createConn(cfg *config.SubTaskConfig, dbCfg config.DBConfig, timeout string
 func createConns(cfg *config.SubTaskConfig, dbCfg config.DBConfig, count int, timeout string) ([]*Conn, error) {
 	dbs := make([]*Conn, 0, count)
 
-	baseConn, err := createBaseConn(dbCfg, timeout)
+	rawDBCfg := &baseconn.RawDBConfig{
+		MaxIdleConns: cfg.SyncerConfig.WorkerCount,
+	}
+	baseConn, err := createBaseConn(dbCfg, timeout, rawDBCfg)
 	if err != nil {
 		return nil, err
 	}
 	for i := 0; i < count; i++ {
 		// TODO use *sql.Conn instead of *sql.DB
 		// share db by all conns
-		bc := &baseconn.BaseConn{baseConn.DB, baseConn.DSN, baseConn.RetryStrategy}
+		bc := &baseconn.BaseConn{baseConn.DB, baseConn.DSN, baseConn.RetryStrategy, rawDBCfg}
 		dbs = append(dbs, &Conn{baseConn: bc, cfg: cfg})
 	}
 	return dbs, nil
diff --git a/syncer/syncer_test.go b/syncer/syncer_test.go
index fdd0cbd84d..190e7877c1 100644
--- a/syncer/syncer_test.go
+++ b/syncer/syncer_test.go
@@ -935,8 +935,8 @@ func (s *testSyncerSuite) TestGeneratedColumn(c *C) {
 
 	syncer := NewSyncer(s.cfg)
 	// use upstream db as mock downstream
-	syncer.fromDB = &Conn{baseConn: &baseconn.BaseConn{db, "", &retry.FiniteRetryStrategy{}}}
-	syncer.toDBs = []*Conn{{baseConn: &baseconn.BaseConn{db, "", &retry.FiniteRetryStrategy{}}}}
+	syncer.fromDB = &Conn{baseConn: &baseconn.BaseConn{db, "", &retry.FiniteRetryStrategy{}, baseconn.DefaultRawDBConfig()}}
+	syncer.toDBs = []*Conn{{baseConn: &baseconn.BaseConn{db, "", &retry.FiniteRetryStrategy{}, baseconn.DefaultRawDBConfig()}}}
 	syncer.reset()
 
 	streamer, err := syncer.streamerProducer.generateStreamer(pos)
@@ -1216,14 +1216,14 @@ func (s *testSyncerSuite) TestSharding(c *C) {
 		syncer := NewSyncer(s.cfg)
 
 		// fromDB mocks upstream db, db mocks downstream db
-		syncer.fromDB = &Conn{cfg: s.cfg, baseConn: &baseconn.BaseConn{fromDB, "", &retry.FiniteRetryStrategy{}}}
-		syncer.toDBs = []*Conn{{cfg: s.cfg, baseConn: &baseconn.BaseConn{db, "", &retry.FiniteRetryStrategy{}}}}
-		syncer.ddlDB = &Conn{cfg: s.cfg, baseConn: &baseconn.BaseConn{db, "", &retry.FiniteRetryStrategy{}}}
+		syncer.fromDB = &Conn{cfg: s.cfg, baseConn: &baseconn.BaseConn{fromDB, "", &retry.FiniteRetryStrategy{}, baseconn.DefaultRawDBConfig()}}
+		syncer.toDBs = []*Conn{{cfg: s.cfg, baseConn: &baseconn.BaseConn{db, "", &retry.FiniteRetryStrategy{}, baseconn.DefaultRawDBConfig()}}}
+		syncer.ddlDB = &Conn{cfg: s.cfg, baseConn: &baseconn.BaseConn{db, "", &retry.FiniteRetryStrategy{}, baseconn.DefaultRawDBConfig()}}
 
 		// mock syncer.Init() function, because we need to pass mock dbs to different members' init
 		syncer.genRouter()
-		syncer.initShardingGroups(&Conn{cfg: s.cfg, baseConn: &baseconn.BaseConn{shardGroupDB, "", &retry.FiniteRetryStrategy{}}})
-		syncer.checkpoint.Init(&Conn{cfg: s.cfg, baseConn: &baseconn.BaseConn{checkPointDB, "", &retry.FiniteRetryStrategy{}}})
+		syncer.initShardingGroups(&Conn{cfg: s.cfg, baseConn: &baseconn.BaseConn{shardGroupDB, "", &retry.FiniteRetryStrategy{}, baseconn.DefaultRawDBConfig()}})
+		syncer.checkpoint.Init(&Conn{cfg: s.cfg, baseConn: &baseconn.BaseConn{checkPointDB, "", &retry.FiniteRetryStrategy{}, baseconn.DefaultRawDBConfig()}})
 		syncer.reset()
 		events := append(createEvents, s.generateEvents(_case.testEvents, c)...)
 		syncer.streamerProducer = &MockStreamProducer{events}
@@ -1362,10 +1362,10 @@ func (s *testSyncerSuite) TestRun(c *C) {
 	s.cfg.DisableCausality = false
 
 	syncer := NewSyncer(s.cfg)
-	syncer.fromDB = &Conn{cfg: s.cfg, baseConn: &baseconn.BaseConn{db, "", &retry.FiniteRetryStrategy{}}}
-	syncer.toDBs = []*Conn{{cfg: s.cfg, baseConn: &baseconn.BaseConn{db, "", &retry.FiniteRetryStrategy{}}},
-		{cfg: s.cfg, baseConn: &baseconn.BaseConn{db, "", &retry.FiniteRetryStrategy{}}}}
-	syncer.ddlDB = &Conn{cfg: s.cfg, baseConn: &baseconn.BaseConn{db, "", &retry.FiniteRetryStrategy{}}}
+	syncer.fromDB = &Conn{cfg: s.cfg, baseConn: &baseconn.BaseConn{db, "", &retry.FiniteRetryStrategy{}, baseconn.DefaultRawDBConfig()}}
+	syncer.toDBs = []*Conn{{cfg: s.cfg, baseConn: &baseconn.BaseConn{db, "", &retry.FiniteRetryStrategy{}, baseconn.DefaultRawDBConfig()}},
+		{cfg: s.cfg, baseConn: &baseconn.BaseConn{db, "", &retry.FiniteRetryStrategy{}, baseconn.DefaultRawDBConfig()}}}
+	syncer.ddlDB = &Conn{cfg: s.cfg, baseConn: &baseconn.BaseConn{db, "", &retry.FiniteRetryStrategy{}, baseconn.DefaultRawDBConfig()}}
 	c.Assert(syncer.Type(), Equals, pb.UnitType_Sync)
 
 	syncer.columnMapping, err = cm.NewMapping(s.cfg.CaseSensitive, s.cfg.ColumnMappingRules)
@@ -1379,7 +1379,7 @@ func (s *testSyncerSuite) TestRun(c *C) {
 	checkPointMock.ExpectExec(fmt.Sprintf("CREATE TABLE IF NOT EXISTS `%s`.`%s_syncer_checkpoint`", s.cfg.MetaSchema, s.cfg.Name)).WillReturnResult(sqlmock.NewResult(1, 1))
 	checkPointMock.ExpectCommit()
 
-	syncer.checkpoint.Init(&Conn{cfg: s.cfg, baseConn: &baseconn.BaseConn{checkPointDB, "", &retry.FiniteRetryStrategy{}}})
+	syncer.checkpoint.Init(&Conn{cfg: s.cfg, baseConn: &baseconn.BaseConn{checkPointDB, "", &retry.FiniteRetryStrategy{}, baseconn.DefaultRawDBConfig()}})
 	syncer.reset()
 	events1 := mockBinlogEvents{
 		mockBinlogEvent{typ: DBCreate, args: []interface{}{"test_1"}},