3D model reconstruction based on parallel contour is a problem distributed in many application fields, which include main matter of correspondence, branch, tilling and fitting. The research situation of branch problem is described in this paper, and a definition is given according to the model features of branch. The contours in the adjacent plane are projected in the same plane, and divided into two classes through the region division method. Algorithm which to calculate the auxiliary branch geometry object is present in this paper with the polygon center line method. Finally, experimental study was carried out in 3D geological modeling, and experiments show that the algorithm in this paper can improve the modeling efficiency and precision.