Abstract: Aiming at complexity and uncertainty of relation between fault characteristics and fault types of mine ventilator,the paper proposed a kind of fault diagnosis method of mine ventilator based on similarity measures of Vague sets.The method makes relation between fault types and fault characteristics vectors and fault characteristics vectors collected to be expressed with Vague sets.Through calculating and comparing similarity measures between Vague sets of fault knowledge and Vague sets of fault samples,it gets results of fault diagnosis.The application example showed that the results of applying the diagnosis method to do fault diagnosis to mine ventilator are coincided with actual situation and the method has some rationality.