At present,the fluctuation of large-scale wind-photovoltaic power output and load increases the demand for operational flexibility in the distribution network. Soft open point integrated with energy storage system (ESOP) contains both the flexible power regulation ability of soft open point and the power storage ability of energy storage system,which can improve the operational flexibility and economy of the distribution network. Firstly,the principle and mathematical model of ESOP are elaborated. Then,two distribution network flexibility evaluation indexes including net load regulation and branch load margin are proposed from the perspective of node and grid flexibility resources respectively,and the distribution network operating costs and ESOP planning and construction costs are proposed as the economic indicators. After that,an optimal planning model with the flexible and economic operation of the distribution network with ESOP as an objective function is established. Finally,the model is solved by the second-order cone programming algorithm. Through the simulation of the modified IEEE 33-bus system,the results show that the proposed flexibility evaluation indicators can accurately quantify the operational flexibility of the distribution network,and the proposed optimal planning model can realize the operational flexibility and economy distribution network.