Abstract: In view of problems of low efficiency, poor accuracy and difficulty in reusing and sharing diagnostic knowledge of traditional fault diagnosis methods of mine hoist, a fault diagnosis method for mine hoist spindle system based on ontology was proposed. In view of diversification of fault causes of mine hoist spindle system, a three-dimensional coordinate method is proposed to summarize various fault phenomena and their causes, and the problems such as incomplete fault summary and unreasonable reason analysis are solved; fault diagnosis ontology library is established through Protégé4.3, and fault phenomenon, fault causes and their corresponding logical relationship are stored in ontology library as knowledge, which solves problems of knowledge sharing and reuse of fault diagnosis, and improves efficiency of fault diagnosis; SQL Server 2008 database is used to access monitoring data of the spindle system, and Java persistence layer application program interface JPA and Java application program interface Jena are used to establish mapping between ontology library and database, so as to realize dynamic data exchange of database and ontology library; finally the monitoring data is analyzed through ontology library to determine fault causes and locate fault sources, and then fault diagnosis is realized. The example analysis results show that the fault diagnosis method for mine hoist spindle system based on ontology improves efficiency and accuracy of fault diagnosis, and has high reliability.