Objective To improve the spraying mode and paint variety of internal surface of ammunition, solve the problems of high environment adaptability of ammunition charge and crack flaw due to low-temperature storage. Methods A high pressure airless spray technique was adopted to carry out spray painting of internal surface of ammunition, to substitute the original air spray mode. The effects of factors such as paint pressure, paint viscosity, nozzle movement speed on the coating quality were discussed, and the optimal process parameters were determined by orthogonal experiments. The situation of the environment adaptability of ammunition charge and the crack flaw of paint film with different thickness were tested by linear accelerator. Results The paint film of inner surface of ammunition had good appearance quality, the thickness of paint film and the adhesion met the requirements when the paint pressure was 65 kg/ cm2, the paint viscosity was 30 s, the nozzle movement speed was 50 Hz, the nozzle diameters were 0. 51 and 0. 71 mm, respectively. The ammunition with a paint film of 180 μm thickness did not crack after the high- and low-tem-perature storage tests. Conclusion It was proved by application that the high-pressure airless spray technique used for horizontal automatic inner surface spraying of ammunition was feasible and worthy of spreading in industry.