Blockchain technology has changed the centralized management model of the existing environmental monitoring system by virtue of its decentralized and non-tampering characteristics. However, with the increase in the amount of monitoring data, the environmental monitoring blockchain system is faced with a large number of computing and communication overhead caused by data consensus, which affects the normal collection, calculation, and upload of environmental monitoring data. Aiming at the above problems, this paper proposes a credit grouping Byzantine fault-tolerant(CGBFT) mechanism which is suitable for environmental monitoring blockchain scenarios. First, the reliability analysis is performed based on the authenticity and integrity of the data transmitted by the monitoring nodes to obtain the credit value of each node as the basis for selecting the master node. Second, the consistency protocol of PBFT is optimized for the characteristics of the environmental monitoring blockchain system to meet the data consensus strategy of high throughput and reliable fault tolerance. The scheme analysis shows that the improved PBFT consensus mechanism can effectively solve the problems of high communication overhead and low efficiency in the system performance.