The working principle of the air pump is: the engine drives the crankshaft of the air pump through two triangle belts, which drives the piston to pump, and the gas is fed into the air reservoir through the airway. On the other hand, the gas in the air reservoir is imported into the pressure regulator fixed on the air pump through a gas duct, so as to control the air pressure in the air reservoir. When the air pressure in the gas reservoir does not reach the pressure set by the pressure regulator, the gas entering the pressure regulator from the gas reservoir cannot open the pressure regulator valve; When the air pressure in the air reservoir reaches the pressure set by the pressure regulator, the gas entering the pressure regulator valve from the air reservoir opens the pressure regulator valve valve, enters the air pump connected with the pressure regulator valve, and controls the air inlet of the air pump normally open through the airway, so as to make the air pump run with empty load, achieve the purpose of reducing power loss and protecting the air pump.