Abstract: The working power transmission of wind turbines is mainly completed by the gearbox. Under impact loads, the output shaft of the wind turbine gearbox generates significant torsional stress, causing fatigue failure and resulting in a high failure rate. Accurately analyzing the load and fatigue life of the output shaft of wind turbine gearbox is crucial for the reliability research of wind turbine gearbox. However, currently the load analysis methods for the output shaft of wind turbine gearboxes mainly rely on simulation, resulting in significant errors compared to actual operating conditions. Therefore, this article takes a 1.5 MW wind turbine gearbox as the carrier, statistically analyzes the actual operating data of its wind farm, uses rainflow counting method and hypothesis testing method to obtain the load law of different loads on the output shaft of the wind turbine gearbox, and predicts its life using structural fatigue life analysis method based on this. The life prediction results meet the design requirements of wind power gearboxes, and the research results are closer to reality, providing theoretical and practical support for the reliability analysis of wind power gearboxes.