Hi ,

So i ll remove the ip helper address from the  interface vlan ( wireless client ) , and just add on the 

wlc , can you brief  how the traffic flow to the back and forth to the dhcp server 

Thanks for your help 

The WLC can proxy or bridge DHCP requests

http://www.cisco.com/c/en/us/support/docs/wireless/4400-series-wireless-lan-controllers/110865-dhcp-wlc.html

Just to add... If you using the WLC as a dhcp server for example, then proxy for that interface needs to be enabled.  Now if you have an external dhcp server, then you can either proxy the dhcp request, like what Peter mentioned, or you can let dhcp request be broadcasted out from the controller like how switches pass dhcp request.  The later, you would need an ip helper to point the broadcast to the dhcp server.  The traffic flow no matter what is the same... if the AP is in local mode, then all traffic including dhcp request will go to the controller and the controller will either proxy or just send that across to the wired side.  If the AP is in FlexConnect and you have local switching enabled, then traffic would not be tunneled to the WLC and the traffic from the client would hit the AP and the AP would place the traffic on the wired side.

-Scott