Abstract: A supersonic flame spraying gun in which liquid fuel and air-oxygen are mixed in chamber to improve combustion stability by flameholder was obtained. The speed and temperature of jet from the gun was measured by the Spraywatch monitor system. The microstructure and properties of the WC-12Co coatings produced by the gun were investigated. The results indicate that the jet speed exceeds 1 300 m/s,and the adjustable range of temperature is 2 302 K to 3 410 K,which an accuracy of adjustment reaches ±50 K. The WC retention rate in the coating increases with the increasing of air and oxygen mixing ratio,and so the hardness of coatings increases. The thickness of the coating obtained by spraying with air-supporting combustion is over 5 mm.