At present, with the large-scale development of wind power technology, the aerodynamic instability of blades especially the stability under special working conditions has become a hot and difficult problem at home and abroad. The aerodynamic stability of feathering wind turbine blades directly affects the safety and reliability of wind turbines under turbulent wind conditions. Aerodynamic damping is an important index of blade stability judgment. In order to investigate the aerodynamic instability characteristics of the blades of feathered wind turbines under turbulent wind conditions, the aerodynamic damping calculation model of the blades of NERL 5 MW wind turbines was established based on the modified blade element momentum theory, Euler-Bernoulli beam model and aerodynamic damping calculation method, and the Kaimal turbulent wind model was adopted for transient analysis. The influence of wind parameters on aerodynamic stability of wind turbine blades and the probability of aerodynamic instability of wind turbine blades are obtained, which provides a reference for aerodynamic stability design and control of large wind turbine blades. The results show that the aerodynamic damping of the feathering blade presents a period of 180° over the whole wind direction, and the wind direction of 25° is relatively dangerous. The greater the wind speed, the more significant the negative aerodynamic damping value, the larger the range of aerodynamic unstable wind direction, and the greater the instability probability. With the increase of turbulence intensity, the lower limit of first order flapping aerodynamic damping decreases obviously, and the probability of aerodynamic instability increases. In turbulent wind conditions, the instability probability of feathering blades outside the plane direction is greater than that in the plane direction, and the instability probability curves of the two directions show similar periodic rules.