Abstract: Relationship between flow conditions and mass diffusion heat-flux of hypersonic thermo-chemical non-equilibrium flows is researched in this article with numerical simulation method.The simulations follow the RAM-CII flight case configurations,including AUSM+-up scheme and LU-SGS method.The results show that,mass diffusion part heat-flux represents the difference of surface catalytic condition,the ratio of mass diffusion part increases when the Mach number increases at the same height and it decreases when the height increases at the same Mach number.