<p>This paper proposes a novel method for calculating damage in fatigue testing of wind turbine blades using machine vision. With the increasing size of wind turbine blades, biaxial fatigue testing has become a significant area of interest in the industry. The traditional damage calculation method, which relies on strain sensors, becomes unreliable when subjected to biaxial load coupling. In the proposed method, machine vision is utilized to obtain the displacement of target points. A static calibration is then performed to establish the relationship between displacement and bending moment, enabling the real-time measurement of bending moment during fatigue testing. The Miner linear fatigue cumulative damage theory is subsequently applied to calculate the equivalent fatigue cumulative damage. To validate the effectiveness of this method, both static and dynamic experiments were conducted. The results demonstrate that this method achieves the required accuracy for detecting damage in wind turbine blade fatigue testing. Moreover, the data obtained through this method exhibits higher accuracy compared to traditional approaches. The proposed method introduces a novel approach to the wind turbine blade testing industry.</p>