China spray gun pneumatic double diaphragm pump uses compressed air as the power, and the air pressure acts on the inner side of the diaphragm through the reversing mechanism. The outer side of the diaphragm and the pump body together form a paint chamber with a variable volume. When the volume of the left coating chamber is changed from small to large, a partial vacuum is generated, and the next one-way valve is opened, and the one-way valve is closed, the paint in the paint bucket enters the left coating chamber under atmospheric pressure, and the volume of the right coating chamber is changed from large to small. The next check valve is closed, the paint creates pressure, and a check valve is opened to discharge the pump body. The double diaphragm pump has two coating chambers on both sides. When one volume is changed from small to large, the other volume is changed from large to small, and the cycle is repeated. Therefore, the double diaphragm pump has two times of material suction and discharge every time, which makes the output efficiency of the pump increase, and the output is relatively stable. Since the ratio of the input pressure of the compressed air to the output pressure of the paint is 1:1, adjusting the input pressure of the compressed air changes the output pressure of the paint.