Energy storage can suppress the voltage fluctuations caused by photovoltaic (PV) generation． This paper discusses the regulation mechanism of distribution networks with photovoltaic power by means of the energy storage from the viewpoint of avoiding voltage violation and establishes an energy storage need assessment model considering the voltage violation and the variable power flow． It also investigates the energy storage needs under the voltage constraints with different influence factors as well as the voltage regulation effects obtained through the energy storage． Then，the relationships between the energy storage configuration capacity and the influence factors(namely PV capacity，the distance between the partial load and the PV access point，and the distance between the PV access point and the nearby substation) are analyzed by simulations，and the peak load shifting effect of the energy storage on the voltage curve indistribution networks is verified． Meanwhile，the specific energy storage capacity and the configuration recommendations in each case are presented by a Matlab/Simulink simulation．