diff --git a/accton/accton_util.py b/accton/accton_util.py
index 26e7c6c..e6b2adc 100755
--- a/accton/accton_util.py
+++ b/accton/accton_util.py
@@ -696,7 +696,7 @@
     return request            
 
 #dpctl tcp:192.168.1.1:6633 flow-mod table=28,cmd=add,prio=281 eth_type=0x800,ip_dst=100.0.0.1,ip_proto=6,tcp_dst=5000 write:set_field=ip_dst:10.0.0.1,set_field=tcp_dst:2000,group=0x71000001 goto:60
-def add_nat_flow(ctrl, eth_type, ip_dst, ip_proto, tcp_dst, set_ip_dst, set_tcp_dst, action_group_id):
+def add_dnat_flow(ctrl, eth_type, ip_dst, ip_proto, tcp_dst, set_ip_dst, set_tcp_dst, action_group_id):
     match = ofp.match()
     match.oxm_list.append(ofp.oxm.eth_type(eth_type))
     match.oxm_list.append(ofp.oxm.ipv4_dst(ip_dst))
@@ -719,6 +719,30 @@
     logging.info("Inserting DNAT flow eth_type %lx, dip %lx, ip_proto %ld, tcp_dst %ld, SetFeild: Dip %lx, tcp_dst %ld, action_gorup=%lx",eth_type, ip_dst, ip_proto, tcp_dst, set_ip_dst, set_tcp_dst, action_group_id)
     ctrl.message_send(request)
     return request
+
+#dpctl tcp:192.168.1.1:6633 flow-mod table=29,cmd=add,prio=291 eth_type=0x800,ip_src=10.0.0.1,ip_proto=6,tcp_src=2000 write:set_field=ip_src:100.0.0.1,set_field=tcp_src:5000 goto:30
+def add_snat_flow(ctrl, eth_type, ip_src, ip_proto, tcp_src, set_ip_src, set_tcp_src):
+    match = ofp.match()
+    match.oxm_list.append(ofp.oxm.eth_type(eth_type))
+    match.oxm_list.append(ofp.oxm.ipv4_src(ip_src))
+    match.oxm_list.append(ofp.oxm.ip_proto(ip_proto))
+    match.oxm_list.append(ofp.oxm.tcp_src(tcp_src))
+    
+    request = ofp.message.flow_add(
+            table_id=29,
+            cookie=42,
+            match=match,
+            instructions=[
+                    ofp.instruction.write_actions(
+                        actions=[ofp.action.set_field(ofp.oxm.ipv4_src(set_ip_src)),
+                                 ofp.action.set_field(ofp.oxm.tcp_src(set_tcp_src))]),
+                    ofp.instruction.goto_table(30)
+                ],
+            buffer_id=ofp.OFP_NO_BUFFER,
+            priority=1) 
+    logging.info("Inserting DNAT flow eth_type %lx, sip %lx, ip_proto %ld, tcp_src %ld, SetFeild: sip %lx, tcp_src %ld",eth_type, ip_src, ip_proto, tcp_src, set_ip_src, set_tcp_src)
+    ctrl.message_send(request)
+    return request
     
 def get_vtap_lport_config_xml(dp_id, lport, phy_port, vlan, vnid, operation='merge'):  
     """
diff --git a/accton/nat.py b/accton/nat.py
index 7696c2a..c9a03ff 100755
--- a/accton/nat.py
+++ b/accton/nat.py
@@ -103,7 +103,7 @@
         msg2=add_l3_unicast_group(self.controller, port=output_port2, vlanid=2, id=0x3000005, src_mac=[0x00,0x00,0x05,0x22,0x33,0x55], dst_mac=[0x00,0x00,0x05,0x22,0x44,0x66])
         ecmp=add_l3_ecmp_group(self.controller, id=0x1000001, l3_ucast_groups=[msg1.group_id, msg2.group_id])
         add_termination_flow(self.controller, 0, 0x0800, [0x00,0x00,0x00,0x00,0x02,0x00], 200, goto_table=28, send_barrier=False)
-        add_nat_flow(self.controller, eth_type=0x0800, ip_dst=0x64000001, ip_proto=6, tcp_dst=5000, set_ip_dst=0x0a000001, set_tcp_dst=2000, action_group_id=ecmp.group_id)
+        add_dnat_flow(self.controller, eth_type=0x0800, ip_dst=0x64000001, ip_proto=6, tcp_dst=5000, set_ip_dst=0x0a000001, set_tcp_dst=2000, action_group_id=ecmp.group_id)
         
         
         input_pkt = simple_tcp_packet(pktlen=100, 
@@ -139,7 +139,84 @@
         #self.dataplane.send(input_port, str(input_pkt))
         #verify_packet(self, str(output_pkt2), output_port2)
         
+class snat_ecmp(base_tests.SimpleDataPlane):
+    """
+    [SNAT ECMP]
+      SNAT (outbound) with ECMP
+
+    Inject  eth 1/1 DA000000000100, SA000000000101, Tag 100, SIP 10.0.0.1, DIP 200.0.0.01, Sport 2000, Dport 2828 [increase DIP]
+    Output  eth 1/3 DA000000000200, SA000000000201, Tag 200, SIP 100.0.0.1, DIP 200.0.0.X, Sport 5000, Dport 2828
+    Output  eth 1/5 DA000000000500, SA000000000501, Tag 5, SIP 100.0.0.1, DIP 200.0.0.X, Sport 5000, Dport 2828
+
+    ./dpctl tcp:192.168.1.1:6633 flow-mod table=10,cmd=add,prio=101 in_port=1,vlan_vid=0x1064/0x1fff goto:20
+    ./dpctl tcp:192.168.1.1:6633 flow-mod table=20,cmd=add,prio=201 vlan_vid=100/0xfff,eth_dst=00:00:00:00:01:00,eth_type=0x0800 goto:29
+    ./dpctl tcp:192.168.1.1:6633 group-mod cmd=add,type=ind,group=0xC80003 group=any,port=any,weight=0 output=3   
+    ./dpctl tcp:192.168.1.1:6633 group-mod cmd=add,type=ind,group=0x22000002 group=any,port=any,weight=0 set_field=eth_src=00:00:00:00:02:00,set_field=eth_dst=00:00:00:00:02:01,set_field=vlan_vid=200,group=0xC80003    
+    ./dpctl tcp:192.168.1.1:6633 group-mod cmd=add,type=ind,group=0x50005 group=any,port=any,weight=0 output=5
+    ./dpctl tcp:192.168.1.1:6633 group-mod cmd=add,type=ind,group=0x22000005 group=any,port=any,weight=0 set_field=eth_src=00:00:00:00:05:00,set_field=eth_dst=00:00:00:00:05:01,set_field=vlan_vid=5,group=0x50005
+    
+    ./dpctl tcp:192.168.1.1:6633 group-mod cmd=add,type=sel,group=0x71000001 group=any,port=any,weight=0 group=0x22000002 group=any,port=any,weight=0 group=0x22000005
+    ./dpctl tcp:192.168.1.1:6633 flow-mod table=29,cmd=add,prio=291 eth_type=0x800,ip_src=10.0.0.1,ip_proto=6,tcp_src=2000 write:set_field=ip_src:100.0.0.1,set_field=tcp_src:5000 goto:30
+    ./dpctl tcp:192.168.1.1:6633 flow-mod table=30,cmd=add,prio=301 eth_type=0x0800,ip_dst=200.0.0.1/255.255.255.0 write:group=0x71000001 goto:60
+    """
+    def runTest(self):
+        delete_all_flows(self.controller)
+        delete_all_groups(self.controller)
+
+        test_ports = sorted(config["port_map"].keys())
+
+        input_port = test_ports[0]
+        output_port = test_ports[1]
+        output_port2 = test_ports[2]
         
+        add_one_vlan_table_flow(self.controller, input_port, vlan_id=100, vrf=0, flag=VLAN_TABLE_FLAG_ONLY_TAG, send_barrier=False)   
+        add_termination_flow(self.controller, 0, 0x0800, [0x00,0x00,0x00,0x00,0x01,0x00], 100, goto_table=29, send_barrier=False)
+        add_one_l2_interface_grouop(self.controller, port=output_port, vlan_id=200, is_tagged=True, send_barrier=False)
+        #Bits 27:24 is for realm id, so unicast group id give 0x2000002
+        msg1=add_l3_unicast_group(self.controller, port=output_port, vlanid=200, id=0x2000002, src_mac=[0x00,0x00,0x00,0x00,0x02,0x00], dst_mac=[0x00,0x00,0x00,0x00,0x02,0x01])
+        
+        add_one_l2_interface_grouop(self.controller, port=output_port2, vlan_id=5, is_tagged=True, send_barrier=False)
+        #Bits 27:24 is for realm id, so unicast group id give 0x2000002
+        msg2=add_l3_unicast_group(self.controller, port=output_port2, vlanid=5, id=0x2000005, src_mac=[0x00,0x00,0x00,0x00,0x05,0x00], dst_mac=[0x00,0x00,0x00,0x00,0x05,0x01])
+
+        ecmp=add_l3_ecmp_group(self.controller, id=0x1000001, l3_ucast_groups=[msg1.group_id, msg2.group_id])
+        add_snat_flow(self.controller, 0x0800, 0x0a000001, 6, 2000, 0x64000001, 5000)
+        add_unicast_routing_flow(self.controller, 0x0800, 0xc8000001, 0xffffff00, ecmp.group_id, vrf=0, send_barrier=False)
+
+        input_pkt = simple_tcp_packet(pktlen=100, 
+                                       eth_dst="00:00:00:00:01:00",
+                                       eth_src="00:00:00:00:01:01",
+                                       dl_vlan_enable = True,
+                                       vlan_vid = 100,
+                                       ip_ttl=64,                                       
+                                       ip_src='10.0.0.1',
+                                       ip_dst="200.0.0.1",
+                                       tcp_sport=2000)
+        output_pkt = simple_tcp_packet(pktlen=100, 
+                                       eth_dst="00:00:00:00:02:01",
+                                       eth_src="00:00:00:00:02:00",
+                                       dl_vlan_enable = True,
+                                       vlan_vid = 200,                                       
+                                       ip_ttl=63,                                       
+                                       ip_src="100.0.0.1",
+                                       ip_dst='200.0.0.1',
+                                       tcp_sport=5000)
+        output_pkt2 = simple_tcp_packet(pktlen=100, 
+                                       eth_dst="00:00:00:00:05:01",
+                                       eth_src="00:00:00:00:05:00",
+                                       dl_vlan_enable = True,
+                                       vlan_vid = 5,                                       
+                                       ip_ttl=63,                                       
+                                       ip_src="100.0.0.1",
+                                       ip_dst='200.0.0.1',
+                                       tcp_sport=5000)
+
+        self.dataplane.send(input_port, str(input_pkt))
+        verify_packet(self, str(output_pkt), output_port)
+        #self.dataplane.send(input_port, str(input_pkt))
+        #verify_packet(self, str(output_pkt2), output_port2)
+        
+"""just for verify it can work after nat ecmp"""
 class l3Route(base_tests.SimpleDataPlane):
     """
     [L3 unicast route]