To solve the problem that Delegated Proof of Stake (DPoS) consensus mechanism has malicious nodes not eliminated in time due to inactive voting and long voting cycle, an improved scheme of DPoS consensus mechanism based on fusing mechanism, credit mechanism and standby witness node was proposed. Firstly, fusing mechanism was introduced to provide the function of negative vote to quicken kicking out evil nodes. Secondly, credit mechanism was introduced to set credit scores and credit grades for nodes, the credit scores and grades of nodes were dynamically adjusted by monitoring the behavior of nodes, therefore the difficulty of obtaining votes for evil nodes was increased. Finally, standby witness node list was added to fill in the vacancy in time after witness right of evil node being cancelled. A test blockchain system based on the improved scheme was built, and the availability and effectiveness of the improved scheme were verified by experiments. The experimental results show that the blockchain based on the improved DPoS consensus mechanism can eliminate the evil nodes in time and is suitable for most scenarios.