Task assignment method plays a key role in manned /unmanned aerial vehicle formation cooperative air combat.Firstlya task decomposition method with constraint of timing sequential was presented.Thenthe task assignment model was established based on the improved Contract Net Protocol (CNP).The task assignment efficiency was enhanced by adopting the acquaintance model.The timing sequence task was processed by adopting the task validity parameter and blackboard mechanism.Finallysimulation was carried out based on the CNP task assignment modelthe result shows the well performance of the task assignment methodwhich can fulfill the requirement of cooperative air combat.