With the promotion of “carbon peaking and carbon neutrality” goals and wide access of renewable energy, the corresponding management and operation complexity of electric power market transaction subject have increased greatly with the dramatically increased number of participants. Power market transaction platform based on blockchain technology is an effective way to solve the safety, efficiency and fairness problems in transaction process. And the consensus mechanism is the key of the blockchain technology in power trading. RAFT is suitable for blockchain with dynamic changes, asynchronous network and node mobility. But it has disadvantages such as easy election disputes and inability to adapt to malicious nodes. Therefore, this paper proposes an improved RAFT consensus mechanism for power transaction blockchain based on credit scoring. The RAFT consensus mechanism is combined with the operation characteristics of power market. And the election disputes and the speed of RAFT master selection are improved by replacing node voting with credit scoring. The adaptability of RAFT to malicious nodes is improved by setting audit nodes for auditing log copy and election results. The above improvements can meet the requirements of effective consistency of cluster nodes and improve the speed and throughput of RAFT consensus mechanism. Finally, the effectiveness and rapidity of the improved RAFT consensus mechanism proposed in this paper are verified by a practical case simulation.