The invention provides a marine disaster early warning expert system based on data mining. The system comprises 7 modules including a marine data base, a data mining module, a marine disaster knowledge base, a knowledge acquisition interface, an inference machine, an explanation module and a marine disaster early warning display interface. Marine data are abundant and various, large-scale complicated marine data are simplified and compressed by adopting a fuzzy clustering rough set attribute reduction method, attribute factor information related to the marine disaster is retained to the largest extent, information containing a large amount of knowledge is obtained by using the data mining, the information containing the knowledge is regularly extracted and treated, and then strategy rules capable of predicting the marine disasters are found out. The strategy rules organize and form the marine disaster knowledge base and the inference machine, knowledge rules and data in the knowledge base are used for inference, heuristic method inference and judgment are conducted simulating experts in the marine area, marine disasters are evaluated, levels of the marine disasters are judged, and an explanation program is combined with an early warning threshold value to send out disaster early warning towards users in a simple and visual mode. The system effectively solves problems of shortage of expert early warning and marine knowledge personnel on the marine disasters, and provides new ways and methods for popularizing scientific marine disaster early warning technology.