Aiming at that general Finite Element Method is difficult to simulate the complex tunnel excavation inducing the second stresses adjusting, the paper proposed the simulation methods combining loading releasing and stress mapping return arithmetic. After the introduction of relative theory, the FEM code has been developed by VC++ . The excavation process of a large section tunnel engineering CRD construction is simulated by the code, the displacements contour, arc top and arc shoulder settlement, horizontal convergence and ground face settlement corresponding to each excavate step have been obtained by the simulation. The regulation of the results are compared with monitoring data, which stated the method is feasible. The simulation has guiding meaning to the tunnel engineering construction.