Spaceborne Synthetic Aperture Radar(SAR) obtains electronic image of the earth's surface using electromagnetic waves. For it is side-looking imaging, SAR image inherently contains geolocation error caused by SAR image acquisition geometry, imaging mode, scattering properties and image formation process. These errors should be considered and corrected for SAR image utilization. Geolocation accuracy of spaceborne SAR image and geometric distortion can be improved and corrected by using prior control point. The system error transfer law of spaceborne SAR image geolocation is analyzed. An improved system error correction model is proposed by combining the system error sources with similar error transfer characteristics. Monte-Carlo simulation results show that the new model has higher correction accuracy of system error.