The invention relates to a precision resistant welding spot-welder which is mainly used for welding enamel wire extraction contacts and minimal work pieces in the manufacturing of electric elements with small coils and comprises main power supply, a welding head and a die; among which, the main power supply which comprises a resistant welding transformer and a power supply control device provides step wave pulse output and outputs suitable current for welding through the power supply control device; the die connects the welding head and the output through the resistant welding transformer and provides welding power. The resistant welding spot welder output by the step wave of the invention reduces the damages to the welding head caused by excessive current which is used for burning the insulating varnish of the enamel wire and prolongs the service life of the welding head.