Gear tooth crack fault signals are very feeble when the crack is in early stage.To extract early gear tooth crack fault feature effectively,the paper puts forward a comprehensive demodulation analysis method. The method integrates the amplitude-envelope demodulation and the phase-demodulation analysis to the char- acter of the concurrence of amplitude-modulation and phase-modulation in actual gear vibration signals.Simu- lation results and actual diagnosis example demonstrate that the comprehensive demodula...