With the deepening of China’s power system reform, the rapid development of distributed power technology and the increasing demand of users for green and low- carbon power,the research of distributed power trading has ushered in a huge opportunity. A transaction mechanism suitable for the day-ahead market of distributed power is studied based on the blockchain technology. It is composed of transaction contract chain and transaction settlement chain. The transaction contract chain realizes the functions of sealed quotation, transaction matching and transaction release, while the transaction settlement chain realizes the functions of electricity metering, electricity fee settlement and transaction result evaluation. A consensus mechanism suitable for the transaction contract chain and a new method of electricity charge accounting suitable for the transaction settlement chain are designed to safeguard the interests of those who abide by the contract and encourage both parties to abide by the contract and reasonably declare the transaction demand. Finally, the feasibility of the trading mechanism is verified by simulation experiment.