Abstract: The retrieval efficiency will fall down due to the increasing numbers of cases in Database in marketing Ontology hased case retrieval system. How to effectively improve the efficiency of case retrieval system is a serious prohlem. A K-means clustering algorithm based on rough set was proposed which can do the clustering work on thousands of marketing cases in Case Retrieval System in order to figure out the center of each cluster. So there is no need to do the similarity work in terms of each case. It is improved through experiment that the methods can largely enhance the performance of case retrieval system.

Key words: Rough set, K-means clustering, Ontology, Case retrieval