The numerical simulation has been carried out to investigate the cold flow and hot flow characteristics for composite structure of cantilever ramp injector and cavity in the supersonic combustion. The structure without cavity and different positions of cantilever ramp injector/cavity combination has been comparative analyzed. It is noted that the combination distance is h=30mm while the total pressure loss is large, but it has a stronger effect of mixed fuel mix and combustion efficiency greater, flow characteristics is the best.