Abstract: To improve the performance of case-based reasoning in reverse osmosis membrane fault diagnosis, the Fuzzy ART network was first used to divide the source case into multiple clusters. Then, the noise cases and the redundancy cases in each cluster were deleted and the outliers were reserved to realize the maintenance of the case base. Finally, this maintenance strategy and case-based reasoning method were applied to the fault diagnosis of the reverse osmosis membrane, and the comparative experiment was carried out by using the historical data of the reverse osmosis membrane fault in a smelter, which verified the advantages of the improved CBR method in the diagnosis accuracy, and the research has certain practical application value.