After the large-scale distributed photovoltaic (DP) is connected to the power grid, the voltage of the power grid tends to fluctuate greatly, resulting in more and more serious power grid losses. At present, the existing power grid loss reduction methods do not consider the reactive power regulation ability of photovoltaic power generation, and the application effect is not ideal. Therefore, a reactive power voltage control loss reduction method with large-scale DP connected to the power grid was designed. Through establishing objective function, setting constraint conditions, analyzing voltage stability by sensitivity analysis method, taking the value with higher sensitivity as the reactive power compensation position, and forecasting the current load to determine the best compensation capacity, so as to realized power grid loss reduction. The experimental results show that the reference voltage of the proposed method tends to 1 pu and is more stable after loss reduction than before. The proposed method can effectively control the change of reactive power according to the distribution characteristics of photovoltaic control access. Compared with other methods, the fluctuation of reactive power is small, showing a good loss reduction effect.