The invention discloses a voltage control device of a power distribution network. The voltage control device of the power distribution network comprises a three-phase voltage detection module (11), an uncontrollable rectification module (12), a direct-current voltage boosting module (13) and a three-phase output module. The voltage control device is connected between a tail end of a secondary side of a power distribution transformer and a user in series during use; the device is in parallel connection with a switch KM; when the three-phase voltage detection module of the device detects that the three-phase voltage is between (200+7) V and (200-10%) and the three-phase current unbalance degree is smaller than 15%, the KM is in a switched-on state, the device is in a short-circuit state; when the three-phase voltage exceeds the national power distribution network standard voltage and the three-phase current unbalance degree is larger than 15%, or one of the conditions is not met, the KM is in a switched-off state, and the device is in a working state; no matter which state the KM is in, a KM2 is in a switched-on state all the time, thereby ensuring that the voltage of the direct-current voltage boosting module is stabilized at 720V and waiting for three-phase output instructions at any time; when the three-phase inverter side is in a short-circuit state, the KM2 is tripped off, thereby ensuring seamless output of the three-phase inverter side during state switching of the KM.