In this paper ,the geostress field of a large area complicated in geological structures was inverted with the stress data of a few measured points by using FLAC3D numerical stimulation and regression analysis. Two types of models were built. One type is a big model without geological structures, which considered the influence of layer thickness, lithology, stratigraphic dip and ground surface fluctuation first, and then corrected the simulation results according to the measured data, and finally got the geostress field without regional structures by regression analysis. The other type is small regional structure models, which paid attention to the influence of depth, fault type and fault throw, or fold type and fold amplitude, and gained the influence range and coefficients of each geological structure to the geostress field. At last, the results of two types were integrated together, and the large area geostress field under complex geological condition was got. According to this method in allusion to a specific example, the principal stress isoline and vector horizontal projection of coal seam roof including three faults and one fold were obtained, which could analyze the stress magnitude and direction. The method above can solve the problem of how to use the stress data of a few measured points to gain a wide range geostress field under complex geological condition, which could also promote the study of geostress field inversion and have certain engineering application value.