The purpose of this paper is to investigate the effects of intake’s compression process of the scramjet on its flight performance. The hydrogen injection to the supersonic cross-flow is considered as the problem configuration. The finite volume solver is developed to simulate the compressible reacting turbulent flow using the proper reaction mechanism as the finite rate chemistry. The combustion efficiency and the drag force are the most important parameters on the scramjet flight performance, and finding the design point to balance the higher combustion efficiency and the lower minimum drag, which depends on the total pressure loss, can be used to optimize the supersonic combustors. The performance of the supersonic intake is considered here using some oblique shock waves with equal flow-deflection angles to compute the combustor’s inlet condition. The variation of combustion efficiency and total pressure loss is presented for different combustor’s inlet conditions. The results are presented for the constant jet to inlet pressure ratios and also for the constant equivalence ratios, in which the last one is much appropriate and utilized to find the optimum design point of the intake and the combustor, for assumed flight condition.