The main working part of the spraying machine is a double-acting pneumatic hydraulic booster pump, and the reversing mechanism is a special form of pilot-type full-air control gas reversing device. After entering the compressed air, when the piston moves to the upper or lower end of the cylinder, the upper pilot valve or the lower pilot valve is operated to control the air flow to instantaneously push the air reversing device to change direction, so that the piston of the air motor makes a stable and continuous reciprocating motion . Because the piston is rigidly connected to the plunger in the paint plunger pump, and the area of the piston is larger than the area of the plunger. As a result, the inhaled paint is pressurized. The pressurized paint is sent to the airless spray gun through the high-pressure hose, and finally the hydraulic pressure is released at the airless nozzle. After instantaneous atomization, it is sprayed to the surface of the object to form a coating film layer.