The invention relates to a reactive power control method for a water-light complementary power station, which is used for grid-connected point voltage control of the water-optical complementary powerstation, and the reactive power support thereof is realized by a hydropower unit and a photovoltaic inverter. When the voltage fluctuates, the inertia of the excitation system is relatively large, theexcitation lag and the reactive power response deviation exist. The deviation is regarded as the reactive power setting of the photovoltaic inverter to compensate the reactive power response deviation. When the excitation system is adjusted, the reactive power output of the photovoltaic inverter decreases gradually, and the grid point voltage is mainly controlled by the hydroelectric excitation system. In order to prevent frequent operation of hydroelectric generating units and photovoltaic inverters, the dead-time range of voltage deviation is set. If the voltage deviation exceeds the dead-time range, the closed-loop control is effective. At the same time, in order to improve the response speed of voltage loop, the final reactive power setting value is obtained by compensating the reactive power loss of the water-optical complementary power station.