The development of hypersonic aircraft is one important aspect of aeronautics and astronautics in 21st century. The scramjet, the engine of hypersonic aircraft, is a key apparatus. In this paper, the laminar finite-rate and turbulence model are applied and the reaction model of seven components and eight equations, which Morreti presented is accepted. The effect of non-equilibrium chemical reaction is considered. When combustion heating equipment is used in the experiment of scramjet, the mass of vapor produced by test medium is investigated through numerical simulation. The investigation shows that the vapor in contaminants has an obvious effect on the performance of scramjet, the last effect of mass of vapor in gas on the performance of scramjet is decided by the initial condition of the flow.