The integrated navigation system, specially the system based on GPS and INS, is a leading trend of navigation technology, and some of typical integrated navigation systems have been developed and tested in the past few years (Farrell, 1998). But due to the complex application circumstance, it is difficult to describe the noise statistical property accurately. In this paper, a modified adaptive filter algorithm is presented for INS/GPS integrated navigation system. At first, an improved Kalman filter and Hinfin robust filter are explicitly represented for INS/GPS integrated navigation system. Meanwhile, a standard for judging that whether the filter trends to divergence is proposed to combine the two methods. Aiming at the detail position/velocity integrated mode, the computer simulation result of INS/GPS integrated navigation show that this method can restrain the divergence effectively and has better adaptive ability