In recent years, distributed photovoltaic (PV) generations has been widely applied. However, when connected to distribution network, PV generation will Cause voltage fluctuations and other problems with the intermittence and randomness of its output power. In order to get a better development of PV generation ,the influences of connecting PV generation to distribution network on voltage fluctuation are analyzed theoretically. And get the conclusion that the fluctuation of output power of PV generation and network short circuit capacity will affect the voltage fluctuation. Considering the increase of PV capacity in the future, the better way to weaken voltage fluctuation is to gain the network short circuit capacity through the loop-close operation of annular network, which is also beneficial for more PV generation to be connected to distribution network and will be a must in the future. The correctness of above-mentioned analysis, which lay the foundation for the great development of distributed PV, is verified by using PSCAD/EMTDC to establish numerical examples of distribution networks with PV generation.