As renewable generation and clean energy source, photovoltaic (PV) generation has a promising prospect. China has now established a number of MW solar power plants. With certain control strategy and under certain operating conditions, PV generation is able to demonstrate good reactive power supporting characteristics for future smart distribution system. This paper has done some preliminary researches in reactive power optimization planning of local distribution system with centralized integration of large-scale PV plants. Based on the operation data of actual PV plants, the case study shows that, to some extent, the overall system voltage level can be improved, thereby reducing system power loss, through the proper coordination of the distribution system with PV plants supplying reactive power and active power injection.