Abstract: Triangulation for stratigraphic interface including reverse faults with overlapping area is a difficult problem in the field of 3D geological modeling. To solve this problem, based on coal seam floor contour map, an automatic triangulation method by adding outer surrounding ring of overlapping area is presented. Based on the idea of dividing the overlapping area in the local area,this method firstly uses fault lines to form some surrounding rings by equidistant extrapolation which enclose each reverse fault with overlapping area respectively, then uses the outer surrounding ring to cut and divide the stratigraphic interface into a parent region with several inner holes and a number of reverse faults with overlapping area surrounded by the outer surrounding ring. Secondly, for every overlapping area, the lines connecting the two end points of fault line are extended to the outer surrounding ring so that the overlapping area is divided into single-connected upper-wall zone and lower-wall zone; the conventional Constrained Delaunay Triangulation is carried out in the upper-wall zone, lower-wall zone and parent zone respectively and then the zones are spliced together. Finally, all the auxiliary outer surrounding rings added before and triangles linked with outer surrounding ring are removed and triangulation network is reconstructed in local area to realize automatic triangulation of reverse faults with overlapping area. According to the results of actual data test, this method can achieve the triangulation of the reverse fault with overlapping area that has not been completely cut off fully automatically.