Abstract: In this paper, we analyse the characteristics of the hybrid navigation system which is composed of an air data computer and an inertial navigation system and is integrated by a Kalman filter. The result of the computer simulation shows that it is possible to obtain a medium accurate hybrid system with use of a low accurate inertial system（10n. m/n. ）.The hybrid system can detect and compensate drifts of gyroes and perform realignment of platform during flying. It is worth to investigate such system more deeply, in the furture.