Abstract: The focal stress field of the Xinfengjiang earthquakes shows that the T-axis constantly trends towards NNE and is nearly horizontal, but the P-axis rotates from 0? to 180癷n a vertical plane perpendicular to the T-axis. Under the N-S horizontal tectonic compression the focal stress field is induced by a left-lateral transform fault at Heyuan resulting from the relative sliding between the rock mass in the reservoir area and on its southern side at different rate.