The invention discloses a novel motor liquid-cooling system, and relates to the field of motor liquid-cooling systems. Currently, the motor liquid-cooling system is mainly in a structure form directlypouring a water outlet passage on an engine seat, the casting process is complicated, the casting finished rate is low, and only the motor can be cooled. The liquid-cooling system assembly comprisesa front end cover, a rear end cover and the engine seat, wherein the engine seat is arranged between the front end cover and the rear end cover, a cover plate is arranged at an outer side of the rearend cover, a controller is arranged at an outer side of the cover plate, a cooling liquid inlet and outlet is arranged on the front end cover, an engine seat water passage loop is arranged on the engine seat, two cooling liquid via holes are formed in the rear end cover, a cover plate water passage is arranged on the cover plate and is used for cooling the controller, and a cooling system loop isformed and is used for cooling the motor body and the controller. Liquid cooling of the motor body and the controller is effectively achieved, the cooling system is more compact in structure, so thatthe motor is more stable and reliable to run, and the motor cost is effectively reduced.