Abstract: According to the specific geological and topographical conditions at dam site of Xiaowan Hydropower Station, fundamental influencing factors and spatial distribution of initial geostress are analyzed. The 3D FEM model and the parameters spatial distribution regression model are built. For each factor, a corresponding calculation is executed with MSC.Marc program. Taking the regression precision as the objective function, the boundary extrusion loads are optimized to simulate the field caused by horizontal compressed tectonic movements. Finally, all parameters of the regression model are estimated. The result of back regression analysis shows that the improved method is available with higher precision, and can simulate 3D initial geostress field more practically. So sa to provide a basis for further exeavating simulation of similar projeets

Key words: Xiaowan Hydropower Station, initial geostress, tectonic movements, spatial distribution model