The apparatus for filling a motor vehicle cooling system includes a communication body, a valve, a flexible connecting hose, a pressure gauge, a relief valve and a hanging portion, in which the valve, the connecting hose, the pressure gauge, the relief valve and the hanging portion are all disposed on predetermined positions of the communication body, while the connecting hose is extended out of the communication body for a distance and it connects to a top opening of the cooling system tightly by a metallic cap.