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