The invention provides a method and system for optimizing a successive load shedding shutdown rule of a pumped storage unit, and belongs to the technical field of hydroelectric generation.The method includes: firstly establishing a successive load shedding transition process simulation model; secondly, performing transition process simulation under different successive load shedding interval timesand operating water heads by utilizing the model, and finding the most dangerous successive load shedding interval time and the most severe operating water head by taking the deviation degree of thewater hammer pressure extreme values of the volute and the draft tube relative to the initial value as an index; and then, setting the simulation model input as a two-stage guide vane closing rule tobe optimized, the most dangerous successive load shedding interval time and the most severe operation water head, and performing guide vane closing rule optimization by taking a double-objective optimization function as an objective under the constraint conditions of control parameters and the objective function to obtain an optimal guide vane closing rule. According to the method, the differencebetween the transition processes of the first-throwing unit and the second-throwing unit during successive load throwing of the units is considered, and multi-unit optimal control is achieved.