Abstract: Based on conquering the shortcomings of conventional qualitative or quantitative fault diagnosis methods for the satellites control system and seeking the new mechanism of combining the qualitative and quantitative method，a new mixed modeling method with the qualitative simulation (QSIM) and the parity space method is proposed. The method achieves the organic combination of the qualitative and quantitative information based on the fuzzy logic. The qualitative/quantitative hybrid model can integrate the system information comprehensively ，and then realize the efficient, accurate and rapid fault diagnosis for the satellite control system. Simulation experiments show that the method is efficient and feasible.

Key words: satellite control system, fault diagnosis, the qualitative/quantitative mixed model, qualitative simulation, parity space