For the deficiency of research and application of the three-dimensional limit equilibrium method，the Hovland improved model and revised Hovland improved model were put forward after modifying the calculating method of vertical force on the element sliding surface in Hovland model and revised Hovland model，whose force analysis is relatively reasonable. Using the GRASS GIS software for the verification of one three-dimensional slope stability analysis，the results shows that when the resolution of grid model is the same the precision of stability factor calculated by improved Hovland models is higher. The slope geologic model construction and stability analysis method based on constraint Delaunay TIN tri-prism elements were presented by introducing Delaunay mesh generation algorithm which can take points，lines，triangle area constraints into consideration. By  adopting the tri-prism slope geologic model，the precision of various calculation models was improved effectively，especially in the case of using Hovland improved calculation models brought up in this paper. Considering the computational efficiency and the balance between calculation accuracy and economy of tri-prism slope geologic model，the research of analyzing the variation of the number of triangles and the stability factor with the minimum triangle area was carried out and the optimal area evaluation index proposed is 1/412–1/206 in Delaunay TIN subdivision. The engineering case study of Heishan open-pit coal mine indicated that the effects of sliding resistance formed in the middle and front of landslide are the main cause leading to high slope safety coefficient in the southern stope.