With the rapid growth of air traffic volume, increasingly crowded airspace operation puts forward higher requirements for the function and performance of navigation system. Aiming at the essential operational requirement of aviation traffic to flight safety, the function and performance requirements of airborne navigation system in different flight stages are discussed on the basis of discussing the airspace operation and navigation function. At the same time, according to the requirements of International Civil Aviation Organization (ICAO) on the accuracy, integrity, continuity, availability and functionality of the navigation system, the airborne Communication, Navigation, Surveillance (CNS) system is further analyzed from the multi-dimensional global view of airborne communication, navigation, surveillance and safety involved in the course of flight. Integration capability and its supporting role in airspace operation. Finally, in order to adapt to the development trend of Performance Based navigation (PBN), the concept of multi-sensor data fusion based on inertial navigation/satellite navigation and the integration and cooperation of space-space navigation are proposed to improve the efficiency of airspace operation and flight safety.