Blockchain systems, with the characteristics of decentralization, irreversibility and traceability, have attracted a lot of attentions recently. However, the current performance of blockchain is poor, which becomes a major constraint of its applications. Additionally, different blockchain systems lack standard performance monitoring approach which can automatically adapt to different systems and provide detailed and real-time performance information. To solve this problem, we propose overall performance metrics and detailed performance metrics for the users to know the exact performance in different stages of the blockchain. Then we propose a performance monitoring framework with a log-based method. It has advantages of lower overhead, more details, and better scalability than the previous performance monitoring approaches. Finally we implement the framework to monitor four well-known blockchain systems, using a set of 1,000 open-source smart contracts. The experimental results show that our framework can make detailed and real-time performance monitoring of blockchain systems. We also provide some suggestions for the future development of blockchain systems.