Two-dimension coupled implicit Navier-Stokes equations and standard k-εviscid model are introduced to simulate the inner and outer flow field of hypersonic vehicle, and the equations are discretized by the second order upwind scheme. When angle of attack is changing from -10°to 7°, the effects of viscosity on the lift, drag force and pitching moment characteristics of hypersonic vehicle in three working conditions including inlet closed, inlet open but unfired, inlet open and fired were discussed. Result shows that the influence is prominent when hypersonic vehicle works under inlet open but unfired、inlet open and fired conditions. especially This case will occur when the drag force characteristic, viscous drag force exceeds 50% of total drag force.