Abstract: For verifying the performances of extended Kalman filter(EKF) and unscented Kalman filter(UKF) in tightly-coupled integrated navigation system,an INS system error model in the earth-centered earth-fixed(ECEF) frame and a GPS pseudo range/range rate model are proposed to form the system equation and the measurement equation respectively,and then EKF and UKF filtering equations are derived.Simulation results validate that EKF and UKF are adequate for the tightly-coupled integrated system,the navigation results of both filters have higher accuracy than a stand-alone GPS receiver,and the two filters have nearly identical performance while the UKF works slightly better.