diff --git a/include/util/taoserror.h b/include/util/taoserror.h
index 65cfe8de0be9e387cecba70141c0bab513d6fc63..3669348a1842fecd82758d02aa7a1367d6cc70af 100644
--- a/include/util/taoserror.h
+++ b/include/util/taoserror.h
@@ -182,8 +182,9 @@ int32_t* taosGetErrno();
 #define TSDB_CODE_MND_BNODE_ALREADY_EXIST       TAOS_DEF_ERROR_CODE(0, 0x0356)
 #define TSDB_CODE_MND_BNODE_NOT_EXIST           TAOS_DEF_ERROR_CODE(0, 0x0357)
 #define TSDB_CODE_MND_TOO_FEW_MNODES            TAOS_DEF_ERROR_CODE(0, 0x0358)
-#define TSDB_CODE_MND_MNODE_DEPLOYED            TAOS_DEF_ERROR_CODE(0, 0x0359)
-#define TSDB_CODE_MND_CANT_DROP_MASTER          TAOS_DEF_ERROR_CODE(0, 0x035A)
+#define TSDB_CODE_MND_TOO_MANY_MNODES           TAOS_DEF_ERROR_CODE(0, 0x0359)
+#define TSDB_CODE_MND_MNODE_DEPLOYED            TAOS_DEF_ERROR_CODE(0, 0x035A)
+#define TSDB_CODE_MND_CANT_DROP_MASTER          TAOS_DEF_ERROR_CODE(0, 0x035B)
 
 // mnode-acct
 #define TSDB_CODE_MND_ACCT_ALREADY_EXIST        TAOS_DEF_ERROR_CODE(0, 0x0360)
diff --git a/source/dnode/mnode/impl/src/mndMnode.c b/source/dnode/mnode/impl/src/mndMnode.c
index 5b8ba6deaa2f768154d90af5b774c098f81c6434..808eac82ac54075fae12ab9b13052b04c1941d91 100644
--- a/source/dnode/mnode/impl/src/mndMnode.c
+++ b/source/dnode/mnode/impl/src/mndMnode.c
@@ -396,6 +396,11 @@ static int32_t mndProcessCreateMnodeReq(SRpcMsg *pReq) {
 
   mDebug("mnode:%d, start to create", createReq.dnodeId);
 
+  if (sdbGetSize(pMnode->pSdb, SDB_MNODE) > 3) {
+     terrno = TSDB_CODE_MND_TOO_MANY_MNODES;
+     goto _OVER;
+  }
+
   pObj = mndAcquireMnode(pMnode, createReq.dnodeId);
   if (pObj != NULL) {
     terrno = TSDB_CODE_MND_MNODE_ALREADY_EXIST;
diff --git a/source/util/src/terror.c b/source/util/src/terror.c
index 575ae10bbbf252cf7235d1746e53bb1ca33404b6..a54d8c2c03487d81a487350ea9261608136233f6 100644
--- a/source/util/src/terror.c
+++ b/source/util/src/terror.c
@@ -187,6 +187,7 @@ TAOS_DEFINE_ERROR(TSDB_CODE_MND_SNODE_NOT_EXIST,          "Snode not there")
 TAOS_DEFINE_ERROR(TSDB_CODE_MND_BNODE_ALREADY_EXIST,      "Bnode already exists")
 TAOS_DEFINE_ERROR(TSDB_CODE_MND_BNODE_NOT_EXIST,          "Bnode not there")
 TAOS_DEFINE_ERROR(TSDB_CODE_MND_TOO_FEW_MNODES,           "Too few mnodes")
+TAOS_DEFINE_ERROR(TSDB_CODE_MND_TOO_MANY_MNODES,          "Too many mnodes")
 TAOS_DEFINE_ERROR(TSDB_CODE_MND_MNODE_DEPLOYED,           "Mnode deployed in this dnode")
 TAOS_DEFINE_ERROR(TSDB_CODE_MND_CANT_DROP_MASTER,         "Can't drop mnode which is master")
 
diff --git a/tests/script/tsim/mnode/basic3.sim b/tests/script/tsim/mnode/basic3.sim
index b0ee23cd8c15e95d26a12659d77fad0ebc0770dc..ab3193e085659b91d1580c45cee7dcd58c0426bc 100644
--- a/tests/script/tsim/mnode/basic3.sim
+++ b/tests/script/tsim/mnode/basic3.sim
@@ -2,14 +2,17 @@ system sh/stop_dnodes.sh
 system sh/deploy.sh -n dnode1 -i 1
 system sh/deploy.sh -n dnode2 -i 2
 system sh/deploy.sh -n dnode3 -i 3
+system sh/deploy.sh -n dnode4 -i 4
 system sh/exec.sh -n dnode1 -s start
 system sh/exec.sh -n dnode2 -s start
 system sh/exec.sh -n dnode3 -s start
+system sh/exec.sh -n dnode4 -s start
 sql connect
 
 print =============== step1: create dnodes
 sql create dnode $hostname port 7200
 sql create dnode $hostname port 7300
+sql create dnode $hostname port 7400
 
 $x = 0
 step1: 
@@ -32,6 +35,7 @@ endi
 print =============== step2: create mnode 2
 sql create mnode on dnode 2
 sql create mnode on dnode 3
+sql_error create mnode on dnode 4
 
 $x = 0
 step2: 
@@ -134,4 +138,5 @@ endi
 
 system sh/exec.sh -n dnode1 -s stop
 system sh/exec.sh -n dnode2 -s stop
-system sh/exec.sh -n dnode3 -s stop
\ No newline at end of file
+system sh/exec.sh -n dnode3 -s stop
+system sh/exec.sh -n dnode4 -s stop
\ No newline at end of file