Abstract: Near-space vehicles encounter significant aerodynamic heating challenges. Liquid films have emerged as a promising thermal protection approach due to their efficient cooling capabilities. This study presents numerical simulations of the liquid film cooling process on an oblique plate at Mach 5. A second-order accurate coupled implicit algorithm is employed to solve the Navier-Stokes equations. The volume of fluid method coupled with adaptive grid refinement is employed to capture the two-phase flow interface and phase interactions, while an evaporation model is implemented to simulate heat absorption during liquid evaporation. The study examines the characteristic flow field structures during the spreading and evolution of the liquid film on the hypersonic oblique plate surface. Furthermore, it investigates the influence mechanisms and trends of coolant mass flow rate, surface tension, viscosity, and plate inclination angle on liquid film cooling performance. The introduction of liquid-phase cooling fluid reduces the wall heat flux on the inclined plate by approximately 40%—87%, which shows a good cooling effect on the wall. Additionally, the wall heat flux reduction coefficient increases with the increase in the mass flow rate, surface tension, and viscosity coefficient of the cooling working fluid, as well as the decrease in the inclination angle of the inclined plate.