As an effective external cooling method, film cooling can significantly reduce the wall temperature of hot end components of aero engines and large liquid rocket engines. With the development of supersonic turbine blade, liquid rocket engine thrust chamber and ramjet thermal protection technology, the impact of shock wave-boundary layer interaction on the cooling effectiveness of film cooling is a problem that must be considered in the engine heat transfer design. In this paper, the two-dimensional supersonic film cooling is simulated based on the plane slot model, and the blowing ratio is similar to the actual engine. Impact of wave structures on film cooling was studied, and flow loss was evaluated by total pressure and entropy parameter to investigate the film cooling efficiency and uniformity distribution. Physical mechanism of shock wave-boundary layer interaction and its impact on film form was revealed. It shows that the shock wave leads to dramatic changes in flow parameters. Boundary layer separation is found due to the shock, and significantly affects the cooling efficiency. The blowing ratio is an important factor affecting the cooling efficiency. With blowing ratio increasing, local film cooling effectiveness and average cooling efficiency are improved and cooling uniformity decreases. However, the shock wave will cause the temperature of the insulation wall to rise, resulting in decreased cooling efficiency.