Abstract: Located in the southeast of Eurasian plate, China mainland is subject to collision, extrusion and subduction of Indian plate, Pacific plate and Philippine Sea plate, so the tectonic stress field there and its dynamical mechanism are very complex. Using a pseudo 3D finite element method and with the orientation and regime indicators from World Stress Map 2008 (WSM2008) database as principal constraints, this paper numerically simulated driving forces onChina mainland andadjacent areas, and estimated the magnitude and direction of plate boundary forces. We analyzed three typical models. The results show that the asthenospheric static push forces have small influence on the tectonic stress field, while the plate boundary forces play a significant role. The collision of Indian plate with Eurasian plate in the Himalayan orogenic belt controls the basic pattern of stress field in China mainland, and is an important cause of lots of strike-slip earthquakes in Sichuan－Yunnan region. The boundary forces of Ryukyu Trench－Nankai Trough subduction zone display push-to-pull segmental feature. Baikal rift is under the action of pull force. Further analysis reveals that in most areas of China mainland the distribution of maximum horizontal shear stress shows a good positive spatial correlation with the radiated seismic energy density in this region.