Abstract:Signal feature extrachon is a key to fault diagnosis. Abrupt signal is often connected with a kind of faults. If abrupt signal can be efficiently recognized, a fault can be diagnosed comparatively easily For how to effectively idenhfy abrupt signals from vibrahon signals with noise, a series of researches is carried out. Research results show that antisymmetric and symmetric wavelet transforms can efficiently recognize abrupt signals, and are really valuable in fault diagnosis.