Abstract: In this paper, the mapping between reference region and physical region is built in advance by harmonic function, and which is extended to the transformation between triangular regions. Then all of the nodal coordinates in physical region are obtained by the numerical solutions of two Dirichlet’s problems through F.E.A. Finally, it is detailed that some sub-regions are combined a real region with joints or holes, according to their top logic relationships. The flow-chart of program and calculating examples are given in this paper.