Abstract: Space-time adaptive processing (STAP) technique can effectively suppress the airborne radar clutter and significantly improve the detection performance of airborne radar for moving targets. However, in engineering application, STAP technique will inevitably be affected by various errors, resulting in performance degradation. In this paper, the mathematical models of various space-time errors are given, firstly. And then, the reason that the errors affect the STAP performance is analyzed systematically from two aspects: the target steering vector mismatch and the increase of clutter degree of freedom. After that, the influence of different errors on the performance of STAP is analyzed with the signal to clutter plus noise ratio (SCNR) loss as the index. Finally, the related analysis is verified by simulation experiments. The research work in this paper quantifies the influences of different errors on the performance of STAP and can provide important theoretical support for space-time error compensation of airborne pulse Doppler radar.