The invention relates to a grid-structure-rigidity-based centralized converter station site selection constant-volume method. The method comprises: S1, calculating a daily total battery conversion demand of electric vehicles in a planned area; S2, calculating a power supply torque index of an urban power grid and carrying out quantitative evaluation on the time-space shifting characteristics of anurban daily power load; S3, constructing a power grid torque balance index of an urban power grid, adjusting the power grid torque balance index to realize minimization, thereby improving the rigidity of the grid structure and obtaining a comprehensive evaluation index of the grid structure rigidity; S4, construct a double-layer multi-target planning model including an upper planning model and alower planning model and determining a constant volume of site selection of a centralized converter station. Therefore, the basic demand of the conversion of the electric vehicles in the area is satisfied; and with utilization of the energy storage property of the centralized converter station for the urban transmission network, overall structural rigidity of the power grid as well as the operation reliability of the grid is improved.