In order to improve the capacity of integration, flexibility and maintainability of communication, navigation and surveillance (CNS) system of large civil aircraft, we research the digital modeling of airborne CNS system. By the development of this modeling simulation, we rapidly realized architecture design, architecture optimization, security index decomposition; simulation of function, performance and interface of CNS system; and analysis of transmission delay and bus operation efficiency in system and in outer system bus. And analyze the advantage of simulation modeling. The analysis results show that this model provides a method for rapid modeling, simulation and architecture design of CNS system, and able to provide input and support for efficient, low-cost realization of designing, development and integration of the next generation of large civil aircraft advanced avionics system in the further.