Abstract: A water-cooled motor includes a housing (10) for accommodating at least a stator (30) and a rotor (40), the housing (10) having a flange (64) on a side wall thereof; an outer casing (60) disposed around the side wall of the housing, the outer casing (60) having a two-start screw thread (63) formed on an internal surface thereof to provide a water inlet channel (81) and a water outlet channel (82) between the housing (10) and the outer casing (60); a water inlet port (61) and a water outlet port (62), both provided on the outer casing (60) and connected to one end of the water inlet channel (81) and one end of the water outlet channel (82), respectively, wherein the other end of the water inlet channel (81) and the other end of the water outlet channel (82) are interconnected at the flange (64).