The regression analysis of stress field is one important method of geostress field back analysis. But if rock stratum geologic origin is complex, the complex geologic origin in simulating initial stress field should be reasonably considered. On the basis of back analysis of stress field of some domestic large  scale mine site, through the assumption of linearity superimpostion and applying different boundary conditions for different geologic origin areas, a regression analysis of stress field is conducted by finite element method. The result shows that results of regression analysis of stress field considering complex geologic origin are in accord with general regularities of geostress field distribution, and the error is apparently less than that of conventional regression analysis of stress field.