The helicopter hydraulic system has characteristics such as wide spreading,complicated structure and multifunction requirements,which make difficult to verity the hydraulic fluid temperature by experiment.The thermal model of typical helicopter hydraulic components was built.Aimed at a specific flight mission,the temperature variation of hydraulic system was simulated and analyzed.Comparisons between results with the flight data prove that the analysis method and the established models are correct and reliable,which can provide basis for design and optimization of helicopter hydraulic system.