Abstract: In order to convert STL model of arteries with open border into a closed model,topology reconstruction,boundary identification and triangulation of arteries were investigated in this paper.First topology structure of STL file was reconstructed using half edge data structure.On this condition,every border segments of STL model can be identified by a process of edge searching.Then constrained Delaunay triangulation with Steiner point insertion was used to triangulate the border regions of STL model.Base on this method automatic software was developed to solve this problem.The results show that this method and corresponding software can convert STL model of arteries with open regions into closed model.It provides necessary foundation to further finite element volume mesh generation and hemodynamic numerical simulation.