Taking a platform in Chenghai sea area as an example, a set of security monitoring system suitable for unmanned offshore platform is designed and developed by using intelligent video monitoring system, automatic identification system of ships, public address and general alarm system, computer monitoring and some other technologies，which realizes the real-time online monitoring of the waters surrounding conditions and the landing place around the platform day and night. The system can intelligently identify illegal ships close to the platform and migrants landing the platform, and automatically trigger sound and light alarms to drive them away. The operation results show that the system can make accurate and timely response to abnormal events, and can automatically trigger associated equipment, thus improving the intelligent level of security monitoring of offshore platforms. This research has certain practical significance for optimizing the security monitoring technology of offshore platforms.