Abstract: Peer-to-peer (P2P) trading is a rapidly developing and novel market mechanism within the distribution network in recent years. Due to the shorter period for investment and construction, the expansion planning of distributed energy resources would be significantly influenced by P2P trading. Considering the gaming and interactions among multiple prosumers, this paper proposes an expansion planning model for distributed energy resources based on the multi-prosumer equilibrium. Then, a distributed algorithm is devised based on the Lp-Box ADMM method considering the model characteristics and solution requirements. The feasibility and effectiveness of the proposed model and algorithm are verified through case studies based on the standard IEEE test system. The impacts of P2P trading and gaming behavior of multiple prosumers on distributed energy resource expansion planning, renewable energy integration, and the costs and benefits of prosumers are further analyzed.