diff --git a/src/util/inc/tref.h b/src/util/inc/tref.h
index 6619ff407e2aad2322e952ce3ef43c87eba64bb2..1ac7cd87bdd8b42580b5ef206fbbf1cdf5ceefa9 100644
--- a/src/util/inc/tref.h
+++ b/src/util/inc/tref.h
@@ -21,15 +21,41 @@
 extern "C" {
 #endif
 
-int  taosOpenRef(int max, void (*fp)(void *)); // return refId which will be used by other APIs
+// open an instance, return refId which will be used by other APIs
+int  taosOpenRef(int max, void (*fp)(void *)); 
+
+// close the Ref instance
 void taosCloseRef(int refId); 
-int  taosListRef();  // return the number of references in system
+
+// add ref, p is the pointer to resource or pointer ID
 int  taosAddRef(int refId, void *p);
+#define taosRemoveRef taosReleaseRef
+
+// acquire ref, p is the pointer to resource or pointer ID
 int  taosAcquireRef(int refId, void *p);
+
+// release ref, p is the pointer to resource or pinter ID
 void taosReleaseRef(int refId, void *p);
 
-#define taosRemoveRef taosReleaseRef
+// return the first if p is null, otherwise return the next after p
+void *taosIterateRef(int refId, void *p);
 
+// return the number of references in system
+int  taosListRef();  
+
+/* sample code to iterate the refs 
+
+void demoIterateRefs(int refId) {
+
+  void *p = taosGetRefNext(refId, NULL);
+  while (p) {
+
+    // process P
+
+    p = taosGetRefNext(refId, p);
+  }
+}
+*/
 
 #ifdef __cplusplus
 }
diff --git a/src/util/src/tref.c b/src/util/src/tref.c
index 4c3b8363407326b724c0b2706231bd751e43e110..23a7210e99105a1e0e9919939da2d6d186e09e26 100644
--- a/src/util/src/tref.c
+++ b/src/util/src/tref.c
@@ -143,8 +143,6 @@ int taosAddRef(int refId, void *p)
     return TSDB_CODE_REF_INVALID_ID;
   }
 
-  uTrace("refId:%d p:%p try to add", refId, p);
-
   pSet = tsRefSetList + refId;
   taosIncRefCount(pSet);
   if (pSet->state != TSDB_REF_STATE_ACTIVE) {
@@ -203,8 +201,6 @@ int taosAcquireRef(int refId, void *p)
     return TSDB_CODE_REF_INVALID_ID;
   }
 
-  uTrace("refId:%d p:%p try to acquire", refId, p);
-
   pSet = tsRefSetList + refId;
   taosIncRefCount(pSet);
   if (pSet->state != TSDB_REF_STATE_ACTIVE) {
@@ -254,8 +250,6 @@ void taosReleaseRef(int refId, void *p)
     return;
   }
 
-  uTrace("refId:%d p:%p try to release", refId, p);
-
   pSet = tsRefSetList + refId;
   if (pSet->state == TSDB_REF_STATE_EMPTY) {
     uTrace("refId:%d p:%p failed to release, cleaned", refId, p);
@@ -305,6 +299,75 @@ void taosReleaseRef(int refId, void *p)
   if (released) taosDecRefCount(pSet);
 }
 
+// if p is NULL, return the first p in hash list, otherwise, return the next after p
+void *taosIterateRef(int refId, void *p) {
+  SRefNode *pNode = NULL;
+  SRefSet  *pSet;
+
+  if (refId < 0 || refId >= TSDB_REF_OBJECTS) {
+    uTrace("refId:%d p:%p failed to iterate, refId not valid", refId, p);
+    return NULL;
+  }
+
+  pSet = tsRefSetList + refId;
+  taosIncRefCount(pSet);
+  if (pSet->state != TSDB_REF_STATE_ACTIVE) {
+    uTrace("refId:%d p:%p failed to iterate, not active", refId, p);
+    taosDecRefCount(pSet);
+    return NULL;
+  }
+
+  int hash = 0;
+  if (p) {
+    hash = taosHashRef(pSet, p);
+    taosLockList(pSet->lockedBy+hash);
+
+    pNode = pSet->nodeList[hash];
+    while (pNode) {
+      if (pNode->p == p) break;
+      pNode = pNode->next;   
+    }
+
+    if (pNode == NULL) {
+      uError("refId:%d p:%p not there, quit", refId, p);
+      taosUnlockList(pSet->lockedBy+hash);
+      return NULL;
+    }
+
+    // p is there
+    pNode = pNode->next;
+    if (pNode == NULL) { 
+      taosUnlockList(pSet->lockedBy+hash);
+      hash++;
+    }
+  }
+
+  if (pNode == NULL) {
+    for (; hash < pSet->max; ++hash) {
+      taosLockList(pSet->lockedBy+hash);
+      pNode = pSet->nodeList[hash];
+      if (pNode) break; 
+      taosUnlockList(pSet->lockedBy+hash);
+    }
+  } 
+
+  void *newP = NULL;
+  if (pNode) {
+    pNode->count++;  // acquire it
+    newP = pNode->p;  
+    taosUnlockList(pSet->lockedBy+hash);
+    uTrace("refId:%d p:%p is returned", refId, p);
+  } else {
+    uTrace("refId:%d p:%p the list is over", refId, p);
+  }
+
+  if (p) taosReleaseRef(refId, p);  // release the current one
+
+  taosDecRefCount(pSet);
+
+  return newP;
+}
+
 int taosListRef() {
   SRefSet  *pSet;
   SRefNode *pNode;
diff --git a/src/util/tests/trefTest.c b/src/util/tests/trefTest.c
index 486f9f6d6d8cbde6f130aebc96efb209c5b26997..09ffccd7b5fc4ea1c2a645a8ff6d8ec0c70cc8f2 100644
--- a/src/util/tests/trefTest.c
+++ b/src/util/tests/trefTest.c
@@ -17,6 +17,19 @@ typedef struct {
   void **p;
 } SRefSpace;
 
+void iterateRefs(int refId) {
+  int  count = 0;
+
+  void *p = taosIterateRef(refId, NULL);
+  while (p) {
+    // process P
+    count++;
+    p = taosIterateRef(refId, p);
+  }    
+
+  printf(" %d ", count); 
+}
+
 void *takeRefActions(void *param) {
   SRefSpace *pSpace = (SRefSpace *)param;
   int code, id;
@@ -44,6 +57,9 @@ void *takeRefActions(void *param) {
       usleep(id % 5 + 1);
       taosReleaseRef(pSpace->refId, pSpace->p[id]);
     }
+
+    id = random() % pSpace->refNum; 
+    iterateRefs(id);
   }  
 
   for (int i=0; i < pSpace->refNum; ++i) {
@@ -63,7 +79,7 @@ void *openRefSpace(void *param) {
   SRefSpace *pSpace = (SRefSpace *)param;
 
   printf("c");
-  pSpace->refId = taosOpenRef(10000, myfree);
+  pSpace->refId = taosOpenRef(50, myfree);
 
   if (pSpace->refId < 0) {
     printf("failed to open ref, reson:%s\n", tstrerror(pSpace->refId));