Abstract: In this paper, the distribution of in-situ stress and the changed stress field after boring are studied. By use of three-dimensioal FEM and a adaptive boundary load, an outlying oil field of Daqing is modeled as an example. The results, including stress direction, the relationslip between stress and depth, are coincident with measured in-situ stress of East China. Then we get a rule that with the same ratio of radius and the distance from hole center, the calculated stresses are same. Based upon these, we enlarged hole radius and use 3-D FEM to calculate the stress around borehole. The changed stress field is coincident with the observed collapse of bore hole.