Abstract: The flow field near the endwall of gas turbine cascade presents extremely complicated three-dimensional characteristics, and the endwall cooling design needs to consider not only the effects of the strong secondary flow of the endwall on the cooling performance, but also the effects of the cooling layout on the flow and heat transfer characteristics of the proximal endwall. In view of the cooling demand for the gas turbine cascade endwall, a combination of numerical simulation and experimental test were used to systematically investigate the effects of discrete air film holes, leakage flow and endwall modification on the endwall surface film cooling, heat transfer, flow and cascade aerodynamic characteristics under different mass flow ratios. The results show that, the film cooling effectiveness of the endwall can be effectively improved by the appropriate injection angle and layout of the film holes, the geometric structure of the leakage flow cooling unit and the addition of micro-scaled ribs on the endwall surface. The leakage flow from upstream slot and rim seal can provide cooling protection for the upstream and the area near the suction surface of the upper half of the endwall, while the leakage flow from mid-passage gap will protect the rear half endwall near suction side well. The arrangement of fan-shaped air film holes and the curved assembly gap can not only improve the effectiveness of film cooling, but also effectively control the aerodynamic losses.