Analysis of the tectonic stress field plays an important role in petroleum accumulation dynamics simulation. The current study on stress field mainly focuses on two-dimensional analysis of the plane. With the development of the three-dimensional simulation of petroleum forming process, three-dimensional numerical simulation of stress field becomes increasingly important. This paper discusses the finite element simulation of stress field and solution of the whole process based on three-dimensional space. After analyzing the finite element method, it puts forward the calculation method based on irregular hexahedral element described by the corner-point grid data model. The three-dimensional finite element method of tectonic stress field, based on irregular corner-point grid data model, is the innovation in this paper.