Abstract: In order to study the flow and combustion characteristics of kerosene fueled rectangular dual-mode scramjet under different flight conditions, the accuracy of the numerical method was verified by direct connect experiment. Three-dimensional steady numerical simulations were carried out for six cases with different equivalence ratio and Mach numbers. The distribution of the wall pressure and the one-dimensional mass average Mach number along the flow direction of the scramjet were given. The characteristics of the shock structure and heat release rate were analyzed. The results show that the scramjet works in two different combustion modes under different flight conditions. When the scramjet is in the ramjet-mode operation, the pre combustion shock trains propagate to the front of the fuel injector, and the shock system in the combustor is relatively weak; as the shock train moves forward, the separation vortex structure is formed in the isolator, and the fuel is rolled up to the upstream. Part of the combustion is completed before the injector. The separation of the combustor mainly occurs inside the cavities, and the heat release is concentrated in the head of the first cavity. When the scramjet is in the scramjet-mode operation without shock train forward propagation, the shock system in the cavity section is relatively stronger and the fluctuation of flow parameters is more severe. The combustion occurs downstream of the injector, and the separation vortex in the combustor has a long flow span, forming a continuous flow separation from the leading edge of the first cavity to the second cavity. The separation vortex helps the combustion to propagate downstream, so the heat release is more evenly distributed along the flow direction of the combustor. The flow separation induced in the section between two cavities promotes the formation of the separation vortex with large flow direction span in the combustor, which may help the combustion to propagate downstream, so as to realize distributed heat release and avoid shock train propagation caused by concentrated heat release.