The invention discloses a bottom plate mounting structure of a motor with a ventilating outer cover. The bottom plate mounting structure comprises a stator shell, a ventilating outer cover, a spacer plate, a T-shaped fixing block and a bottom plate, wherein the ventilating outer cover is arranged on the outer part of the stator shell; a square hole is formed in the ventilating outer cover and contacted with the surface of the stator shell; the spacer plate is positioned in the square hole, and one end of the spacer plate is contacted with the surface of the stator shell; a T-shaped straight slot is formed in the stator shell; the T-shaped fixing block is positioned in the T-shaped straight slot of the stator shell; a threaded hole used for mounting screws is formed in the middle of the T-shaped fixing block; a through hole used for enabling the screw to pass is formed in the middle of the spacer plate, and the through hole and the threaded hole of the T-shaped fixing block are positioned on the same straight line; and the screws are sequentially screwed into the bottom plate, the through hole of the spacer plate and the threaded hole of the T-shaped fixing block, so that fixed connection between the bottom plate and the stator shell is realized. According to the bottom plate mounting structure disclosed by the invention, the motor fixing stability can be improved, and fluctuation of transmission performance is reduced.