A lot of research result indicate optimization design of backoff mechanism and contention window can improve performance of IEEE802.11 DCF MAC. Based on the formation of small UAVs, the information flying satellites and IEEE802.11, an optimized MAC mechanism was proposed: DCF/CCW.A station estimated the number of competing terminals through monitoring the channel, and used constant contention window. This mechanism is of topology, the system contention code obtained from monitoring channel changes with network configuration. Thereby it can adjust optimal constant contention window dynamically. The analysis results indicate when network scale is definited, system throughput have more effect on contention window, and less effect on system access delay. The optimized mechanism can develop and improve the communication performances of the cooperative network.