As to the fault diagnosis difficulty caused by the fact that fault feature is possible not obvious in mechanical transmission system,a method based on variational mode decomposition and FCM is proposed for gearbox condition monitoring. Firstly,the state data of the gearbox is decomposed into different modes,and the singular value of each mode is used as the feature value,and the state is identified by fuzzy clustering. The results show that the fault identification rate is above 86% for the gearbox fault of artificial unable to identify,and the condition monitoring based on the method can provide reference for the gear fault warning and severity.