According to the nonstationarity and nonlinearity of the broken teeth fault of gear

the Hilbert-Huang transform is employed.Firstly

the a series of Intrinsic Mode Functions（IMFs） are obtained by the Empirical Mode Decomposition （EMD）method.Secondly

the Hilbert transform is executed to every IMF

and the Hilbert spectrum is obtained.The method is applied into the analysis on the gear fault signal of factory and the characters of the broken teeth fault are extracted

furthermore

the number of the broken teeth and their severity are forecasted.The results show that the presented method is beneficial to the diagnosis of gear faults in field practice.