How to determine the in-situ stress field available for the engineering practice is an urgent practical problem of the geotechnical engineering. In tests, different boundary loads are exerted on the 3-D FEM geological model of Qingyuan Pumped Storage Power Plant in order to simulate the in-situ stress owing to diverse influence factors. And then on the basis of the field measured in-situ stress data, in-situ stress field in the whole rock mass including the major project locations is obtained by the inversion method of multivariate regression.