A reactive power allocation method for multiple grid-connected photovoltaic inverter systems comprises three-level reactive power optimization control. The method comprises: performing real-time measurement of a voltage at a point of common coupling of a power station; and acquiring, by means of PI control, an amount of reactive power required for maintaining the voltage, and performing reactive power optimization in order to minimize losses of the station, thereby greatly reducing reactive power control costs. The invention realizes precise control on reactive power output in a station and reduces costs for a system.