Using 40 mechanism solutions of earthquake focus and 3 synthetic solutions of small earthquake, the crustal stress field in and around Gansu region is discussed. The directions of P-axes from the western area to the southeastern area changed from N40°E to N90°E step by step. The horizontal directions of P-axes are vertical to the northeast edge of Tibet Plateau, and the elevation angles of P-axes are less than 30°. It will be shown that the power source of this region is caused by the collision between India and Eurasia plate. The change of regional stress field is of great value for discussing the fault activity.