In connection with the problem that it is difficult to get the accurate fatigue life of BEV transmission gears because of lacking for established load spectrum,based on instantaneous road conditions UDDS conditions,taking vehicle parameters as input,by using simulation modeling method,a method of obtaining contact stress- time of BEV two speed transmission gears is proposed finally. A new calculation method of contact stress is proposed through analyzing stress features of gear,the fatigue load spectrum is obtained by using the new method,the contact fatigue life of BEV two speed transmission gears is predicted based on the nominal stress method and fatigue cumulative damage theory finally. The results show that calculated fatigue life value of gears satisfies the designed fatigue life of BEV transmission.