Based on the real working conditions,the gear oil viscosity for 350 km/h EMU gearbox was calculated with elastic fluid lubrication empirical formula，the gear oil type was determined through the simulation of EMU gearbox steady temperature field by finite element method.Considering the ambient temperature,the low temperature performance requirement was got.The agreeable gear oil type was determined by considering the viscosity requirements,the high temperature oxidation resistance and low temperature requirements,which provide theories for the EMU gear oil selection and design.