The systematic error of InSAR is composed of orbit error and long-wavelength atmospheric delay,which is one of the most important factors that affect the accuracy of InSAR deformation monitoring.Traditional method models the systematic error of each individual interferogram in spatial domain,so it is difficult to distinguish between the long-wavelength deformation and systematic error.In this study,we modeled the systematic errors in spatio-temporal domain,determined the weight matrix of the observations according to its quality,and estimated the deformation parameters and systematic error by the weighted least square method.The simulation results show that,even in the extreme cases where the spatial characteristics of deformation and systematic error are completely consistent,the proposed method can separate the deformation and systematic errors effectively.The deformation rate RMSE of the proposed method is 98.8% lower than that of traditional method.The experiment with ASAR shows that,the proposed method and traditional method obtain similar results when the deformation scale is small and scattered over the study area.However,when large scale long-wavelength deformation occurs in the study area,the results obtained by the proposed method are more robust than those obtained by traditional method.