Traffic control is an effective measure to increase the capacity of junctions to alleviate traffic conges-tion． A class of these approaches deals with coordination of traffic lights in order to allow vehicles traveling in a giv-en direction to pass an arterial without stopping at junctions． Using multi-agent technology，a coordinated traffic signal control algorithm based on cooperative mediation is proposed． The coordination of traffic control is modeled asa distributed constraint optimization problem． The optimal asynchronous partial overlay( Opt APO) which is a coop-erative mediation based DCOP protocol is used to obtain the optimal strategy． The simulation results show that astrategy which can minimize the global costs can be obtained from the coordinated traffic signal control algorithmbased on cooperative mediation．