At present, the maintenance of key equipment for domestic and foreign offshore oil drilling platforms generally adopts the mode of planned maintenance and temporary repair, which is less sensitive to failure signs, and emergency shutdown due to sudden failures often brings huge economic losses. Therefore, it is urgent to explore new maintenance management strategies that can meet the actual needs of the platforms. This article discusses the drawbacks of preventive maintenance and the shortcomings of the existing conditional maintenance concept, introduces the concept of smart maintenance, and develops an intelligent maintenance system for key equipment of offshore platforms based on real-time online monitoring of equipment, with functional business as the main line and multi-source data as the driver. Based on fault diagnosis and early warning theory, the system can evaluate the status of platform equipment and provide reasonable maintenance suggestions. At present, the system has been successfully used to assist platform maintenance personnel in the maintenance and repair of top drive, main engines and thrusters, etc. Application results show that the system’s alarm accuracy and diagnosis accuracy reach 97.51% and 90%, respectively, which effectively reduces maintenance costs and improves maintenance efficiency and quality.