To optimize the operation of shared energy storage, this study investigates the non-cooperative game problem in transactions between shared energy storage and multi-prosumer. First, a bi-level optimization model is established to characterize the non-cooperative game relationship among the participants, aiming to optimize the trading strategies of the shared energy storage operator and the prosumers. The upper-level model maximizes the operator’s profit by optimizing its operational schedule and pricing strategy to provide charging and discharging services. The lower-level model responds to these prices by minimizing each prosumer’s operational cost through optimizing their electricity trading and storage schedules. This approach helps the operator optimize trading strategies and enhance both market competitiveness and profitability. Next, the Karush-Kuhn-Tucker (KKT) conditions are applied to transform the bi-level problem into a single-level model. The reformulated model is linearized using the big-M method and then solved numerically. Finally, simulation results demonstrate that the proposed method effectively balances the interests of both the shared energy storage operator and the prosumers, achieving a mutually beneficial outcome.