A method for evaluating the operational flexibility of a power distribution system with a high proportion of distributed generation (DC) belongs to the technical field of evaluating the operational flexibility of a power distribution system. The method analyzes relevant factors that affect the operational flexibility, determines load scenarios based on an improved fuzzy C-means clustering algorithm in view of the voltage constraints of a distribution network, and proposes a calculation method of an operational flexibility quantitative evaluation index in consideration of the probability of theload scenarios, in order to acheive the spatial and temporal evaluation of the operational flexibility of the power distribution system with a high proportion of DG. The index can reflect the flexibility status and change of the system in operation, as well as the effect of an energy storage device in improving the operational flexibility of the power distribution system.