Abstract: Taking the helical gear transmission of pure electric vehicle reducer as the research object, the possible energy loss of helical gear transmission during rotation is simulated and analyzed based on Amesim simulation software. A pair of helical gear simulation models and a mathematical model of energy loss simulation based on different gear parameters are established, and some calculation methods are given to calculate the energy loss. A new SKF equation is used to calculate the friction torque of both sides of the helical gear bearings. The PID speed control method is used to provide the required speed. The simulation results show that the model can simulate all kinds of energy loss and total loss in the process of helical gear rotation very well. Through setting different helical gear parameters, a set of data with the lowest total loss is found, which provides a basis for optimizing gear parameters and gear design.