Pneumatic spot welding machine

The invention provides a pneumatic spot welding machine. The machine comprises an electric welder box; a lower bracket on which a lower electrode is mounted is arranged at the side part of the electric welder box; a cylinder bracket is mounted at on the top part of the electric welder box; a cylinder is mounted at the end part of the cylinder bracket; a piston rod of the cylinder is downwards arranged; an upper electrode is mounted on the piston rod of the cylinder and is positioned right above the lower electrode; the upper electrode, the lower electrode and the cylinder are all connected with a controller; the movement track of the upper electrode is changed from the arc-line movement into the straight-line movement; three convex points on a steel cap are all in contact with a steel plate; when the current is increased or the welding time is prolonged, the phenomenon that electrodes are adhered, or a workpiece is seriously ablated, or welding points have large burr dot no occur; clearances between the steel plate and the steel cap can be removed, thus the welding firmness can be obviously improved, and the problem that turning easily occurs after a plug is synthesized can be solved; operators can directly operate the machine through a controller, so that the labor intensity of the operators can be effectively reduced.