Abstract: In this paper, the focal mechanism solutions of moderate and small earthquakes in north China and the tectonic stress field is analyzed. The focal mechanism solutions are calculated using the initial motion method and the amplitude ratio method. The results show that the focal rupture of the moderate and small earthquakes in north China is mainly composed of strike-slip faults. According to the nodal plane sliding angle and P axis and T axis angle, the main source of stress is in the horizontal direction. The direction of the main compression stress P axis is NEE-SWW.