The numerical calculation of YX3 small motor external cooling system was carried out by using computational fluid dynamics method. The influence of blade main structure parameters on the ventilation performance of external cooling fan of small motor was analyzed. From the perspective of reducing the input power of the fan, the fan structure was improved and experimentally verified. The result showed that mechanical loss of the motor with improved fan was reduced by 39.1%, the temperature didn’t change basically and the efficiency was increased by 0.6%.