Abstract: The N-S equation and RNG k-ε turbulence model are adopted to analyze the internal flow field of the side wall compression hypersonic inlet and its isolator for RBCC engine.The main point is focused on the effect of cowl position on the flow field and the related phenomena with a free stream Ma=6.The results show that if the cowl position relative to the throat section is moved forward,it has greater effect on the degrees of flow homogeneity at the outlet section than the cowl aft-positioned case.The effects on the total compression ratio,the intense of the cowl shock, the captured mass flow rate and the total pressure recovery are also greater.