A motor cooling structure, including: branch flow-channels, shell flow-channels, end cover flow-channels, a liquid inlet and a liquid outlet. A plurality of the branch flow-channels are circumferentially arranged on a stator of a motor around an axis of the motor. The shell flow-channels includes a liquid inlet flow-channel, a plurality of shell long flow-channels and a liquid outlet flow-channel, which are circumferentially arranged on a reducer shell around the axis of the motor. The end cover flow-channels includes a plurality of the end-cover long flow-channels are circumferentially arranged on a motor end cover around the axis of the motor. The shell flow-channels, the plurality of branch flow-channels and the end cover flow-channels form a continuous total flow-channel. The liquid inlet and liquid outlet both disposed on the reducer shell are in communication with the liquid inlet flow-channel and liquid outlet flow-channel, respectively.