The vacuum booster is an important part in the braking system. The vacuum booster is a cavity with a larger diameter, and there is a diaphragm (or piston) with a push rod in the middle, which separates the cavity into two parts. One part is connected to the atmosphere, and the other part is connected to the engine intake pipe through a pipe. The vacuum booster uses the principle of inhaling air when the engine is working, resulting in a vacuum on one side of the booster, and the pressure difference relative to the normal air pressure on the other side, using this pressure difference to enhance the braking thrust. Therefore, if the vacuum booster is normal, just a slight step on the brake pedal can generate a considerable thrust, thereby braking the rotating wheels