Abstract: For the problem of harmonic pollution of underground power network caused by existing mine-used three-phase power supply, a mine-used digital three-phase power supply based on STM32F103VB was designed and working principle and control strategies of the power supply were introduced in details. A typical AC-DC-AC structure is adopted in the power supply. The voltage-current dual closed loops direct current control strategy is used in PWM rectifier to make input current and input voltage in phase, input current in sine and output voltage in stabilization. The dual closed loops control strategy of outer voltage loop and inner current loop is used in PWM inverter to improve quality of the output voltage waveform and load adaptability. SPWM wave is generated through underflow interruption of TIM1 of STM32F103VB.The experimental results showed that the power supply has high power factor of input and high stability of output with little harmonic of input current.