The traditional centralized transaction mode has some defects, such as high operating cost and information insecurity, when dealing with high frequency and small amount of electricity transaction in microgrid cluster. Therefore, this paper proposes a distributed electricity transaction model of microgrid cluster applying blockchain technology, and designs the corresponding smart contract. Firstly, for the deficiency that unified pricing charging method of network fee is not fairly allocated to each transaction according to the actual operating cost of distribution network, a dynamic network fee model considering multiple operation costs of distribution network is proposed on the basis of power transfer distribution factors. Secondly, in order to ensure the preference of market subjects, an objective strategy function of power purchase considering user credit preference is established, and the improved particle swarm algorithm is used to solve matching process of transaction. Thirdly, this paper adopts self-adaptive aggressive strategy to update the quotation for transaction efficiency, and proposes the multi-round rolling constraint checking method to maintain safe operation of distribution network. Ultimately, the relevant case studies verify the rationality of the proposed model and smart contract.