Abstract: The implementation of distributed peer-to-peer (P2P) energy trading facilitates the localized balancing of the power supply and demand, leading to an improvement in grid utilization efficiency whilst ensuring fairness. A P2P energy trading model was proposed, and a cooperative surplus distribution mechanism building on the asymmetric Nash bargaining theory was studied. First, a cooperative model was established to enable cooperation between sellers and buyers in a P2P energy trading system, offering cooperative surplus due to cooperation. Then, by using the asymmetric Nash bargaining theory, a profit distribution model for both parties was constructed to ensure the equitable allocation of the cooperation surplus among buyers and sellers. Finally, case studies were presented to verify the effectiveness of the proposed model. The simulation results indicate that the cooperative method can improve the benefits of each entity and the overall benefits of the cooperative alliance. It reflects the disparity in contributions between sellers and buyers within the P2P energy trading system, thereby enabling a fair distribution of cooperation surplus.