Based on gear system dynamics

nonlinear dynamics fault model on gear tooth crack is proposed firstly in consideration of the factors such as friction and eccentric mass.By the numerical solution and simulation analysis

the conclusion is that fault feature is more prominence in turning signal than vibration signal.Compared different working condition of model including rotate speed and load

the better working condition is found for easy picking up the fault feature.The result revealed the principle and character of vibration response under fault model

and offered academic base for obtaining better signal to faults diagnosis.By experiment the result proves that this method can break a new path for improving accuracy of faults diagnosis about gear tooth.