Abstract: The monitoring and earlywarning information system of marine radioactive environment in the North China Sea was developed to meet the demand of monitoring and early warning of marine management department. The system includes three parts: information database, analysis and evaluation module and early warning module. The system implements the management of radioactive monitoring data and automatic evaluation and analysis, and the information management of nuclear accident early warning, simulation prediction of emergency response, information transmission and information notification. Some functions of the system had been applied in the radioactive monitoring voyage after establishment of the system. It shows that the system has greatly improved the work efficiency and provided technical support for the marine radioactive monitoring and early warning.