Abstract: Energy storage is an important element affecting the secure operation of smart distribution networks. This paper proposes the dispatchable region model for the urban active distribution network with energy storage to describe the secure operation range of the system with the participation of energy storage. Firstly, the different roles of energy storage are analyzed from the perspective of distribution network security. The security service time and the real-time security service capability of energy storage are defined in order to quantify the security services of energy storage in the distribution networks. Secondly, taking the load and the distributed generation output as the state variables of the security analysis, the dispatchable region model is established considering the capacity and voltage constraints. The model shows that the dispatchable region with energy storage has the new characteristics of time-varying and uncertainty. Thirdly, an analysis-simulation method is used to solve the model, which gives attention to both the efficiency and accuracy. The analytical expressions of the region considering voltage constraints, network loss and real-time states of energy storage are obtained. Finally, through the implementation of two cases, the effects of energy storage on security are represented in the form of regions, revealing the functional mechanism of energy storage on the dispatchable region and the application of the dispatchable region, which gives a planning suggestion that energy storage is suitable to be configured downstream of the feeders.