The invention provides a cooling device for a water pump of a motor. The cooling device comprises the water pump, a water collection device arranged in front of the water pump and a pumping pipe arranged behind the water pump. The water collection device comprises a casing with the inner portion communicated with the water pump. A water inlet pipe group communicated with the inner portion of the casing is arranged on the casing. A valve plug driven by a power device and provided with a water inlet valve plug is arranged in the casing. The valve plug is a valve shaft driven by the power device and moving in the casing, and the water inlet valve group is a valve block group fixed on the valve shaft. Due to the valve block group, the whole weight is reduced, the torque of the power device needed by the cooling device during work is reduced, responsiveness of the whole device is improved, resistance borne by cooling liquid in the water collection device is reduced, and friction loss is small. Meanwhile, the invention further relates to a motor cooling system with the cooling device and a vehicle with the motor cooling system.