diff --git a/spark-on-angel/mllib/src/main/scala/com/tencent/angel/spark/ml/tree/gbdt/helper/SplitFinder.scala b/spark-on-angel/mllib/src/main/scala/com/tencent/angel/spark/ml/tree/gbdt/helper/SplitFinder.scala
index 10b3414f4..c1e0899ef 100644
--- a/spark-on-angel/mllib/src/main/scala/com/tencent/angel/spark/ml/tree/gbdt/helper/SplitFinder.scala
+++ b/spark-on-angel/mllib/src/main/scala/com/tencent/angel/spark/ml/tree/gbdt/helper/SplitFinder.scala
@@ -98,6 +98,7 @@ object SplitFinder {
     var curFlow = -1
     var curSplitId = 0
     val edges = ArrayBuffer[Float]()
+    edges += splits(0)
     edges.sizeHint(FeatureInfo.ENUM_THRESHOLD)
     val binGradPair = if (param.numClass == 2 || param.isMultiClassMultiTree) {
       new BinaryGradPair()
diff --git a/spark-on-angel/mllib/src/main/scala/com/tencent/angel/spark/ml/tree/split/SplitSet.java b/spark-on-angel/mllib/src/main/scala/com/tencent/angel/spark/ml/tree/split/SplitSet.java
index ea2c7c86a..beb5a00ab 100644
--- a/spark-on-angel/mllib/src/main/scala/com/tencent/angel/spark/ml/tree/split/SplitSet.java
+++ b/spark-on-angel/mllib/src/main/scala/com/tencent/angel/spark/ml/tree/split/SplitSet.java
@@ -26,6 +26,8 @@ public class SplitSet extends SplitEntry {
 
   private float[] edges;
   private int firstFlow;
+  // edges=[x,...] firstFlow=1 => go to right if < x and go to left if > x
+  // edges=[x,...] firstFlow=0 => go to left if < x and go to right if > x
   private int defaultFlow;
 
   public SplitSet() {