Film cooling was modeled to allow performance prediction of scramjet engine design. The model was based on experimental results of the compressible mixing layer for the vicinity of the injection slot, and on analytical results of the turbulent boundary layer in the region far from the slot. The film cooling model was integrated with a quasi-one-dimensional scramjet performance prediction model. In an engine employing a combination of film cooling and regenerative cooling, coolant flow rate of the engine slightly exceeded the stoichiometric flow rate, even at high flight Mach numbers, and had the best specific impulse and system pressure performances. These advantages were achieved by an increase in the volume flow rate and a decrease in the velocity difference between the main flow and the coolant, both due to an increase in the film coolant temperature. The effective cooling system with a combination of film cooling and regenerative cooling was also advantageous with regard to avoidance of excess cooling of the engine wall.