The peak-valley effect on the network load is increasing along with the increasing load of the distribution network. And the large-scale renewable energy which was combined to the grid has great impact on the power grid. They have serious effect on the reliability and economy of the working of power grid. The application of energy storage technology for the distribution network can not only reduce the investment in response to the increase of load peak, but also promote the development and the exploitation of renewable energy, which does a favor for the reliability and quality of power supply. The energy storage system (ESS)as the technical support to intelligent distribution network plays a more and more important role. In this paper, the advantages of ESS applied to power distribution network was evaluated from the point of the perspectives of the network update delaying, network damage reducing, reducing backup power for distributed generation, the reducing of reliability cost, etc. The effect of ESS on the voltage of distribution network was theoretical derived. so the result would provide supporting evidence to the optimization analysis on the locating and capacity of ESS, which produces the important reference for the ESS configured in the distribution network.