Abstract: The "Opinions on Further Improving the Pricing Mechanism for Pumped Storage Power" issued by the National Development and Reform Commission in 2021 established a two-part tariff mechanism, which has significantly accelerated the rapid development of China′s pumped storage industry. However, for pumped storage projects serving inter-provincial mutual assistance, current policies have yet to clarify the recovery pathways and cost-sharing mechanisms for inter-provincial capacity fees. This oversight has led to a mismatch between costs and benefits in practice, not only constraining the cross-provincial service efficiency of pumped storage stations but also hindering the integration of renewable energy. Against the backdrop that regionally coordinated allocation of pumped storage stations proves more economical than province-specific allocation, this study proposes a capacity fee-sharing scheme based on the "avoided cost method." Through an avoided cost analysis framework and the theory of public goods value realization, the study systematically demonstrates the scientific validity and rationality of this cost allocation method, which has been proved by empirical cases. The method not only aligns with the "beneficiary pays" principle of cost allocation but also effectively captures the actual value flow in inter-provincial mutual assistance scenarios.