Missile boarded CAN bus has strict requirements for real-time characteristic. Based on an air-to-ground missile control system, CAN bus network was designed. Serial transmission delay, hardware interface delay and media access delay are main reasons of bus delay. Media access delay of the network was studied with non-preemptive priority queuing theory model. Actual CAN bus network simulation shows that this network work well under 800kbps and 1000kbps Baud rate, with maximum delay time 508µs and 292µs, respectively. The delay time is far less than the minimum 10ms periodic, meeting the real-time requirements.