This series of AC spot welder collocates with precise welding controller, precise controls to the welding current and welding time, welding transformer and the electrode all has water cooling function, greatly lengthened the welder’s using life-span, provides with the welding current monitor, and can test and control to the welding current. Widely applies in professions in machinery, hardware, automobile, electric appliance and so on, may reliable welding.to the plate and the rods.