Gears are among the most common mechanical equipment and components, it will directly affect the operation of the equipment. The paper summarizes and analyzes the mechanism and gear fault vibration characteristics, detailed introduces the gear vibration signal analysis and fault diagnosis method, and application of the wavelet packet de-noising to deal with gear fault vibration signal.Gear fault vibration signals are stationary signal, with conventional Fourier analysis method to reach the good effect. Wavelet analysis method can also from both in time domain and frequency domain analysis of signal, very suitable for gear fault diagnosis.Wavelet packet analysis in recent years is rapid development of a fault diagnosis method, the signal in image processing and communication and geophysical research achievements have been made in application of success. Wavelet packet transform is wavelet transform, the promotion was composed of wavelet analysis. This paper around the wavelet transform and wavelet packet transform in gearbox fault diagnosis in theory and experiment, the wavelet packet analysis method is applied to the gear fault diagnosis. Main content as follows:1 from the theory of fault signal characteristics and diagnosis of the fault signal wavelet packet analysis is the inherent requirement of diagnosis,2. Secondly, studied wavelet analysis and wavelet packet analysis based on the theory of noise principle and model analysis,3 studied wavelet packet analysis in signal de-noising in actual application of the signal, wavelet packet decomposition and de-noising and achieved good results,4 studied wavelet packet decomposition in frequency feature extraction in the practical application, through the analysis that the method can be very good characteristics extracted information, carries on the diagnosis malfunction,Based on wavelet packet of signal decomposition and reconstruction of high resolution capability, the signal is decomposed into different frequency band, and then choose effective fault signal reconstruction, isolate the fault information. Through the gear fault signal de-noising and decomposition, shows that this method can effectively remove the noise interference, extract fault feature of signal, the gear fault diagnosis.