The invention relates to a motorcycle water pump cover with a possible function, which comprises a cover body, wherein a water cavity is arranged on the inner wall of the cover body; the water cavity becomes larger and larger and is shaped like an involute; a water inlet tap and a water outlet tap are arranged on the cover body; an impeller matched with a water pump shaft is arranged at the outer top of the water cavity; a plurality of back blades are arranged on the impeller to form an involute helicoids; the center of the impeller corresponds the inner hole of the water inlet tap; a mounting hole is formed in the top of the cover body; an observation window is mounted in the mounting hole; the observation window comprises a ring-shaped frame and a transparent baffle plate; a mounting groove is formed in the inner side wall of the ring-shaped frame in the circumferential direction; the transparent baffle plate is clamped in the mounting groove; a rubber layer is stuck to the outer side wall of the ring-shaped frame; the outer diameter of the rubber layer is greater than the diameter of the mounting hole; and the outer wall of the rubber layer is stuck to the inner wall of the mounting hole and is in sealing fit with the inner wall of the mounting hole. The water pump cover adopting the structure can avoid water leakage of the water taps, improves the water pumping capacity, and ensures the water cooling effect of an engine. Besides, the condition in the water cavity can be observed via the visual window, and the water pump cover has the characteristics of simple structure, convenience in assembly and low cost.