Abstract: A high power transistor-inverter power source controlled by a TP801 single-board computer,which can be used as the power source of resistance spot welding or resistance seam welding,is described in this paper.The research was concentrated on the inverting,the controlling of the constant current and the protecting of the components.The basic work principle and structure,the concrete circuit,the control and the protection of the inverter power source were studied so as to provide a good basis for developing this new resistance welding power source and to make some technical proparation for developing resistance welding robot.The research results indicate that this power source is succeeded in inverting and the control protaction system could make the main circuit work perfectly,and the inverter has good properties.