The utility model relates to a pair of pneumatic robot welding tongs, which comprise a bracket component, a fixed welding arm, a main cylinder, a movable welding arm and a transformer, wherein the movable welding arm is installed at the front end of a piston rod of the main cylinder, and the transformer and the welding tongs are installed into a whole body. The pneumatic robot welding tongs have the advantages that the transformer and the welding tongs are installed into a whole body, a water-supply cable between the transformer and a welding electrode is canceled, failure rate is reduced, the volume of equipment is reduced, the production cost of the welding tongs is effectively reduced, a floating component comprising the main cylinder and the fixed welding arm floats relative to the bracket component, and when the welding electrode is worn or the dimension of a work piece has error, the error is compensated, and the welding quality is ensured; and the elasticity of a balancing spring is balanced to the gravitation of the floating component, the distortion of the work piece is reduced when being clamped, and the welding precision is ensured.