A photovoltaic inverter steady-state model is built to analyze the operation control relationship of inverter and the reactive power regulation of single-stage and two stage inverters operated in different conditions. Aimed to compensate the reactive power of PV power plant connected to grid, the reactive power control strategy is given. And the photovoltaic power plants P-λ curve is analyzed to save cost for reactive power compensation device costs and reduce line losses. The effectiveness and practicality of the given control strategy is evaluated based on an actual PV power plant in Qinghai Province.