Abstract: The un-linear error model with GPS/INS has been built,and the UPF has used to make the function of position of integrated navigation realized.In order to solve the problem of the non-positive definite of estimation error covariance in UKF,the positive processing has been adopted.In additional,MCMC has been adopted to decrease the particles impoverishment.The experiment results show that:UPF has better accuracy than UKF and EKF,and the fluctuation of the error is rather small,which make the accuracy and robust requirements of the navigation system on satisfied.