Abstract: In order to meet the requirements of micro-parts for precision,rapidity and stability of welding energy,a high frequency transistorstyle resistance spot welding power supply was designed. The power supply includes a half-bridge inverter constant current charging part and a high-frequency chopping output part. The inverter frequency is 100 k Hz,the PWM and the incremental PID control technology was used to achieve constant current charging for capacitor group rapidly. The chopping frequency is 100 k Hz,so the control accuracy and response speed of welding output energy was greatly improved. The experimental results show that the maximum charging current of the capacitor group is 100 A,the charging voltage is 30 V and the charging time is less than 100 ms. The power supply has a constant current,constant voltage and constant power output mode. The rising speed of welding current reaches up to 10 A/μs and the output discharging pulse can be stable within 1 ms,the actual welding effect is good,and there are obvious advantages in precision welding.