Abstract: The hard ware and software of a developed 8098 single-chip microcomputer controlled MOSFET precise spot welding power source have been introduced in the paper. The power source can be used in precise spot welding of bridge band and others such as metallic foil and wire. It can delivers arbitrary special and complex current waveform by accurate controll of current instantaneous value. So that the welding of different dimensions and materials workpieces in optimum current waveform can be achieved. An industrial PC has been used to monitor and manage the welding process and various parameters. That raises welding quality and automatic level further. The actual welding production showed that the power source can meet the strict requirments of high quality bridge band spot welding and it is an ideal precise spot welding power source.