Abstract: High velocity thermal spraying as a new technology has the characters of high velocity and high quality.This paper introduced the principle,characters and the application of this technology and reported the design and investigation of the spray gun,analyzed the structure characters of the six kinds of international popular guns.Also it discussed the change rules of the pressure,velocity and temperature of the flame and the particles use numerical simulation.So,it provided a foundation for designing the spray gun and developing the technology of the high velocity thermal spraying.