An electric water pump including a rotor assembly, wherein the rotor assembly includes an iron core body having a central through-hole, a plurality of magnetic plates disposed inside the iron core body, a first plastic coating layer for enclosing the iron core body, and a second plastic coating layer. At least one protruding rib is provided on a top surface and/or a bottom surface of the first plastic coating layer, a recess matching the protruding rib is provided on the second plastic coating layer, and the first plastic coating layer can drive the second plastic coating layer to rotate relative to an axis of the central through-hole of the iron core body.