The invention discloses a grounding fault arc extinguishing method and a device based on a controllable voltage source. The method comprises the following steps: continuously measuring three-phase voltage, zero-sequence current and zero-sequence voltage; When the fault is detected, the fault phase is judged according to the three-phase voltage. The voltage, line-to-ground capacitance, leakage resistance, fault grounding resistance, arc suppression coil inductance, resistance and internal resistance of controllable voltage source in normal operation of fault phase are obtained, and the output voltage of controllable voltage source is calculated. The output voltage of the controllable voltage source is output by SPWM or SVPWM modulation algorithm. By connecting the voltage source, the present application is easier to control and can effectively compensate the fault current and extinguish the arc at the fault point without considering the problem that the inductance parameter of the arc suppression coil and the capacitance of the line to ground are close to the power frequency resonance. The invention calculates the phase and amplitude of the output voltage, realizes the current extinction at the fault point by controlling the amplitude and phase of the controllable voltage source, and ensures the safe and stable operation of the power network and the failure point not to cause fire and other accidents.