diff --git a/rill-flow-dag/olympicene-core/src/main/java/com/weibo/rill/flow/olympicene/core/model/mapping/IterationMapping.java b/rill-flow-dag/olympicene-core/src/main/java/com/weibo/rill/flow/olympicene/core/model/mapping/IterationMapping.java
index 752c0a45..bf0c5551 100644
--- a/rill-flow-dag/olympicene-core/src/main/java/com/weibo/rill/flow/olympicene/core/model/mapping/IterationMapping.java
+++ b/rill-flow-dag/olympicene-core/src/main/java/com/weibo/rill/flow/olympicene/core/model/mapping/IterationMapping.java
@@ -29,15 +29,18 @@
 public class IterationMapping {
     private String collection;
     private String item;
+    private String index;
     private String identity;
 
     @JsonCreator
     public IterationMapping(
             @JsonProperty("collection") String collection,
             @JsonProperty("item") String item,
+            @JsonProperty("index") String index,
             @JsonProperty("identity") String identity) {
         this.collection = collection;
         this.item = item;
+        this.index = index;
         this.identity = identity;
     }
 }
diff --git a/rill-flow-dag/olympicene-traversal/src/main/java/com/weibo/rill/flow/olympicene/traversal/runners/ForeachTaskRunner.java b/rill-flow-dag/olympicene-traversal/src/main/java/com/weibo/rill/flow/olympicene/traversal/runners/ForeachTaskRunner.java
index 073a7636..30b812a2 100644
--- a/rill-flow-dag/olympicene-traversal/src/main/java/com/weibo/rill/flow/olympicene/traversal/runners/ForeachTaskRunner.java
+++ b/rill-flow-dag/olympicene-traversal/src/main/java/com/weibo/rill/flow/olympicene/traversal/runners/ForeachTaskRunner.java
@@ -112,9 +112,7 @@ protected ExecutionResult doRun(String executionId, TaskInfo taskInfo, Map<Strin
             Map<String, TaskInfo> taskInfoMap = TaskInfoMaker.getMaker().makeTaskInfos(foreachTask.getTasks(), taskInfo, groupIndex);
             Set<TaskInfo> subTaskInfos = new HashSet<>(taskInfoMap.values());
 
-            Map<String, Object> subContext = Maps.newConcurrentMap();
-            subContext.putAll(input);
-            subContext.put(iterationMapping.getItem(), item);
+            Map<String, Object> subContext = buildSubContext(input, item, iterationMapping, groupIndex);
             // record whether the subtask is key
             if (existKeyExp(taskInfo)) {
                 for (TaskInfo subTaskInfo : subTaskInfos) {
@@ -146,6 +144,17 @@ protected ExecutionResult doRun(String executionId, TaskInfo taskInfo, Map<Strin
         return ExecutionResult.builder().taskStatus(taskInfo.getTaskStatus()).subTaskInfosAndContext(readyToRun).build();
     }
 
+    private static Map<String, Object> buildSubContext(Map<String, Object> input, Object item,
+                                                       IterationMapping iterationMapping, int groupIndex) {
+        Map<String, Object> subContext = Maps.newConcurrentMap();
+        subContext.putAll(input);
+        subContext.put(iterationMapping.getItem(), item);
+        if (StringUtils.isNotEmpty(iterationMapping.getIndex())) {
+            subContext.put(iterationMapping.getIndex(), groupIndex);
+        }
+        return subContext;
+    }
+
     private boolean isKeySubTask(String executionId, Map<String, Object> subContext, TaskInfo it) {
         return !stasher.needStash(executionId, it, subContext);
     }
diff --git a/rill-flow-dag/olympicene-traversal/src/test/groovy/com/weibo/rill/flow/olympicene/traversal/ForeachTaskTraversalTest.groovy b/rill-flow-dag/olympicene-traversal/src/test/groovy/com/weibo/rill/flow/olympicene/traversal/ForeachTaskTraversalTest.groovy
index d4d28581..d1727e55 100644
--- a/rill-flow-dag/olympicene-traversal/src/test/groovy/com/weibo/rill/flow/olympicene/traversal/ForeachTaskTraversalTest.groovy
+++ b/rill-flow-dag/olympicene-traversal/src/test/groovy/com/weibo/rill/flow/olympicene/traversal/ForeachTaskTraversalTest.groovy
@@ -198,6 +198,7 @@ class ForeachTaskTraversalTest extends Specification {
                 "  iterationMapping:\n" +
                 "      collection: \$.input.segments\n" +
                 "      item: segmentUrl\n" +
+                "      index: subIndex\n" +
                 "  outputMappings:\n" +
                 "    - target: \$.context.gopUrls\n" +
                 "      source: \$.output.sub_context.[*].gopUrl\n" +
@@ -210,6 +211,8 @@ class ForeachTaskTraversalTest extends Specification {
                 "       inputMappings:\n" +
                 "          - target: \$.input.segmentUrl\n" +
                 "            source: \$.context.segmentUrl\n" +
+                "          - target: \$.input.subIndex\n" +
+                "            source: \$.context.subIndex\n" +
                 "       outputMappings:\n" +
                 "          - target: \$.context.gopUrl\n" +
                 "            source: \$.output.gopUrl\n" +
@@ -262,8 +265,8 @@ class ForeachTaskTraversalTest extends Specification {
                         ((DAGCallbackInfo) event.data).context == ['url': 'http://test.com/result', 'segments': ['gopUrl1', 'gopUrl2'], 'gopUrls': ['gopResultUrl2', 'gopResultUrl1']]
         })
         1 * dispatcher.dispatch({ it -> it.taskInfo.name == 'A' && it.input == ['url': 'http://test.com/test'] })
-        1 * dispatcher.dispatch({ it -> it.taskInfo.name == 'B_0-B1' && it.input == ['segmentUrl': 'gopUrl1'] })
-        1 * dispatcher.dispatch({ it -> it.taskInfo.name == 'B_1-B1' && it.input == ['segmentUrl': 'gopUrl2'] })
+        1 * dispatcher.dispatch({ it -> it.taskInfo.name == 'B_0-B1' && it.input == ['segmentUrl': 'gopUrl1', 'subIndex': 0] })
+        1 * dispatcher.dispatch({ it -> it.taskInfo.name == 'B_1-B1' && it.input == ['segmentUrl': 'gopUrl2', 'subIndex': 1] })
         1 * dispatcher.dispatch({ it -> it.taskInfo.name == 'C' && it.input == ['gopUrls': ['gopResultUrl2', 'gopResultUrl1']] })
     }