A variable-frequency voltage-regulating three-phase power supply system was designed. Based on the general-purpose inverter，it realized the output of digital three-phase variable-frequency voltage-regulating sine wave. It possessed the closed-loop control function on the output voltage and could output 0V–380V at 200 Hz–450 Hz，and the output power could reach 30 kW. The system was operated through virtual instrument control panel based on the Programmable Logic Control(PLC)，which held such functions as the frequency measurement，Root Mean Square(RMS) voltage and current measurement，the protection of over-current，the under-voltage and the phase-lacking etc.