The significant progress in information technology has accelerated the rapid development of social manufacturing (SM), making performance monitoring a crucial aspect of SM management. Nonetheless, it encounters issues regarding low trust among participants and centralization in the management platform. Blockchain is a new decentralized infrastructure and distributed computing paradigm that verifies and executes business logic based on smart contracts. Although blockchain has been applied to SM to ensure credibility and decentralization, there is a lack of research on smart contracts for blockchain systems to achieve performance monitoring in SM. Therefore, in the paper, a smart contract model was designed to meet performance monitoring in SM, specifically, a manufacturing promise model was developed to define the specific composition of relative elements in the performance promise between participants, and then a state transfer rule model was established to describe state change rule for the manufacturing promise. Next, a smart contract model for performance monitoring in SM was designed based on the established models. Finally, the model is validated through a case study of SM to produce air-conditioning compressor valves, the results show that the smart contract model is efficient in monitoring the performance states in SM. The model can help the managers in SM monitor the real-time performance conditions and ensure the production plan is completed on schedule.