Abstract: In order to analyze the yaw instability mechanism,based on the yaw torsional vibration model of a small wind turbine,the yaw instability conditions are obtained. By establishing the rigid-flexible coupling model of the wind turbine,the forced vibration analysis is carried out,and the effects of wind turbine yaw speed,tower torsional stiffness and yaw resistance on its vibration characteristics are studied. The results show that the yaw speed has a certain influence on its yaw stability. Increasing the tower torsional stiffness can significantly improve the yaw vibration response,and the application of yaw resistance can not effectively reduce the yaw vibration response of small wind turbines.