Abstract: The broken tooth failure of wind turbine gearbox is one of the main reasons for wind turbine shutdown, which seriously affects the economic benefits and operation safety of wind farms. In this paper, the physical mechanism, characteristics and diagnosis methods of gear tooth broken faults are systematically studied. Through theoretical analysis and experimental verification, the influence mechanism of factors such as dynamic load, assembly error and lubrication failure on tooth broken faults is revealed, and the evolution model of tooth broken faults is established. Experimental results show that the diagnosis accuracy rate of this method for broken tooth faults reaches 98.7%, which is more than 15% higher than the traditional method. The research results provide reference for health monitoring and preventive maintenance of wind turbine gearboxes.