Abstract: With the continuous grid connection of intelligent devices on the user side in distribution systems and the promotion of electricity market reform, more and more power users have changed from traditional consumers to prosumers who can generate electricity, making the peer-to-peer（P2P） power trading between end users possible. In this context, an event-driven P2P power trading market mechanism and its clearing method are proposed, which can effectively consider the operation constraints of distribution systems. Firstly, the relationship between the P2P market and the current power market is discussed, and the eventdriven rules and market operation mechanism are preliminarily established. Secondly, the sensitivity is used to describe the influence of P2P trading on the power system operation. Then, the market clearing optimization model is established, and the Lagrange multiplier method is used for distributed clearing. Thirdly, a fully decentralized P2P power trading market mechanism is realized based on the blockchain platform. Finally, an example is given to verify that the proposed model can deal with the demand of P2P power trading between power communities in distribution systems quickly and effectively on the premise of protecting the safe operation of distribution networks.