Abstract: With a flight simulation system of large civil aircraft developed by the Simulation Research Division at the Beijing University of Aeronautics and Astronautics, this paper introduces its hardware composing and network topology. The distribution of the simulator cockpit, the functions and distribution in the network system of some subsystems including modeling and managing computer, visual system, instrument system, acoustic system, interface system, instructor control computer, and flight management computer have been introduced. The software structure of the modeling and managing computer has been described. Then some key techniques in net communication and real-time property of the system have been discussed.