Abstract: A new concept was raised and adopted to enlarge the scope of two-dimensional model particularly in dealing with three dimensional normal injection cases.Meanwhile,the method has a very good performance in terms of time consuming.The new idea was realized through special disposal with the continuity equations,i.e.,mass flow are added in the source term of the continuity equation.To prove the robustness of this simplified method,in accordance with the test condition published in the literature,calculation was carried out.Calculating results compared with three dimensional programs prove to be satisfactory.A model scramjet combustor tested on the free-jet scramjet test facility was demonstrated and undergone numerical calculation with the two-dimensional program adopted theabove injecting simplification.To simulate the chemical reaction process in thescramjet tunnel,a 5-specise,single step reaction model was introduced.The major aerodynamic parameters and components mass fraction distribution within the model combustor channel were presented.This makes it easy to observe and analyze the flow field.Comparisons of wall pressure between the numerical and experimental results prove the adequate accuracy of the calculation model.