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Engineering practices have shown that the stability of tunnel supports have remarkable time-characteristics. Taking Fang Doushan tunnel as an example, stresses of the primary support, anchor axial force and contact laminating between primary support and secondary lining were surveyed and analyzed. Numerical model used 3D-finite element program was built and the time-stability of tunnel support was analyzed, and the excavation step method was used to simulate the time-stability of tunnel support. The excavation processes are: (1) simulated the initial condition of surrounding rock, (2) excavated the first step, (3) excavated the second step, and then constructed primary support of the first step, (4) excavated the third step, and then constructed the secondary lining of the first step and primary support of the second step, and so on. The simulation results of the section which distance to the opening is about 10 m were analyzed. The results of site survey and numerical simulation showed that the tunnel support was stable.