Entrance is the keystone part of a tunnel and is very difficult to be protected. The dynamic finite element program is employed to simulate the explosion shock wave propagation in typical wall-arch tunnel with uniform section. Some parameters are simplified via assumptions. In course of a numerical simulation, the shock wave pressure value in the tunnel rises to the maximum straight in a moment. Then, due to the reflection back and forth along the inner surface, multi-peak appears, which is different from the ideal shock wave by exponential decay in the free atmosphere. More, the outdoor large-scale model test is tried on with the similar ratio as 1/5, including three-level quantities 0.8kg, 0.6kg and 0.4kg TNT. It further reveals the pressure propagation laws in the tunnel. And at the same time this article gives the fitting empirical formula of the peak pressure by dimensional theory according to the measured test data. The result shows that the fitting test is consistence with the numerical simulation and other empirical formulas.