The main working part of the spraying machine is a double-acting pneumatic hydraulic booster pump, and the reversing mechanism is a special-type pilot-operated full air-controlled gas distribution reversing device. After entering the compressed air, when the piston moves to the upper end or the lower end of the cylinder, the upper pilot valve or the lower pilot valve is actuated, and the control airflow instantaneously pushes the valve of the gas distribution and reversing device, so that the piston of the air motor is stably and continuously reciprocated. .Since 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. The pressurized paint is thus pressurized. The pressurized paint is conveyed to the airless spray gun through a high-pressure hose, and finally the hydraulic pressure is released at the airless nozzle, and is instantaneously atomized and sprayed onto the surface of the object to be coated to form a coating layer.