Abstract: To ensure the intrusion-tolerant availability and reliability of data, the blockchain system is required to use Byzantine fault-tolerant algorithm to replicate data, to avoid the unavailability of data or even loss of data caused by attacks from intrusion nodes. For mode quorum Byzantine fault-tolerant algorithm, a Q/U-GD algorithm is proposed to achieve smooth degradation in high concurrency scenarios. Q/U algorithm is optimized with the Similarity-of-Message （SOM for short）mechanism by Q/U-GD algorithm.The designed SOM reduces the trigger of unnecessary repair operations by enhancing the similarity of messages received by clients and replica nodes. The smooth degradation of performance is realized. The experiment results show that the throughput of Q/U-GD algorithm degrades smoothly in high concurrent scenarios, and is significantly higher than that of Q/U.