Abstract：Crustal stress field is one of the basic content of studying geomechanics and rock mechanics, whose size, orientation, distribution and the history of evolution is the main contents in the study of ground stress in oil and gas exploration. In the process of researching crustal stress, the determination of the regional boundary condition is not only difficult but also is key. Taking the third section of Wumishan, Ren Qiu oil filed as example, putting the regional boundary loads as the unknown condition, target well’s ground stress as constraints condition, based on the multivariate linear regression method，the regional boundary conditions are identified, the regional boundary loads are made out by using matlab. The results show that the crustal stress based on polybasic linear regression is consistent with the actual measurements.