Aiming at the problem of inertial navigation system (INS) failure without timely detection, a fault detection algorithm combining receiver autonomous integrity monitoring (RAIM) and autonomous integrity detection extrapolation (AIME) is proposed. Virtual pseudoranges are equivalently replaced by satellite pseudoranges calculated by inertial navigation, and detection statistics are constructed and detection thresholds are set to detect inertial navigation faults. The simulation results show that the algorithm can effectively detect the fault of inertial navigation and improve the fault detection ability of integrated navigation system.