The invention provides an automatic voltage control device and a control method for a distributed photovoltaic power station. The control device comprises a communication management module, a command processing module, an AVC module, a data management module and an information displaying module. The communication management module is in charge of receiving and transmitting real-time information with a connected device. The command processing module is in charge of converting formats of remote regulation and remote control orders received and transmitted by the communication management module. The AVC module is used for carrying out reactive power control on photovoltaic inverters of the whole station and an SVC/SVG system through the preference control strategy of the inverters according to the real-time information received at present and can control tap positions of a transformer substation, and therefore the busbar voltage of the current power station meets the requirement of power grid dispatching.