In order to improve the judgment ability to face huge amount of equipment defect information and enrich the technical means of defect processing, a method based on FP-growth algorithm for secondary equipment defect analysis in substation is proposed. A defect model is designed for secondary device and FP-growth algorithm is used to find the association rules for secondary device, defects and defect reasons. Through the analysis of the actual defect data of State Grid Corporation, it shows that the proposed method can effectively find the relationship among substation, secondary device, defect properties, defect causes and other factors, and provide valuable information for efficient control and operation of secondary device.