The invention relates to the technical field of plasma spray coating, in particular to a plasma spraying gun. The plasma spraying gun comprises an anode, a gun barrel, a cathode assembly, a backseat, an air inlet pipe and a powder inlet pipe, wherein the gun barrel is connected between the backseat and the anode, the anode is of an annular hollow structure, and is provided with an anode cooling chamber, a first cooling water inlet pipe and a first cooling water outlet pipe, the first cooling water inlet pipe and the first cooling water outlet pipe are communicated with the anode cooling chamber, inner walls of the anode define a spraying chamber, the first cooling water outlet pipe sleeves the powder inlet pipe and is communicated with the anode cooling chamber, the cathode assembly is connected with the backseat, the front end of the cathode assembly stretches into the gun barrel and is opposite to the anode, the air inlet pipe is communicated with an inner chamber of the gun barrel, the cathode assembly is provided with a cathode cooling chamber, a second cooling water inlet pipe and a second cooling water outlet pipe, the second cooling water inlet pipe and the second cooling water outlet pipe are communicated with the cathode cooling chamber, and the second cooling water outlet pipe sleeves the air inlet. The plasma spraying gun can make full use of generated heat energy, and can reach a better spray coating effect.