Abstract: To meet the operation demand of a sharp increase in unit regulation frequency under the Automatic Generation Control (AGC) mode of the new-type power system, and solve the fatigue damage problem of key transmission components such as the operating frame and the rocker arm of large-scale axial-flow Kaplan turbine runners caused by long-term high-frequency alternating stress, a systematic study was conducted on fatigue prevention and control as well as emergency disposal of key runner components. Based on actual crack fault cases of key runner components at Shawan and Angu Hydropower Stations on the Dadu River, a three-dimensional simulation model of the operating frame and the rocker arm was established using ANSYS Workbench finite element software. The fatigue characteristics of core components under AGC conditions were analyzed in detail, structural weak areas were identified, and targeted optimization schemes were proposed. To address extreme working conditions with failure of the runner transmission mechanism, an emergency strategy for fixed-pitch operation of Kaplan runners was put forward. Specific implementation points were clarified from the aspects of feasibility demonstration, blade angle selection, regulation mode adjustment, blade positioning technology, and operation & maintenance control, forming a full-process technical system of "fatigue analysis–structural optimization–emergency disposal". The research results provide technical support for the safe and stable operation of axial-flow Kaplan runners under AGC mode, and have important engineering guiding significance for fatigue damage prevention and emergency disposal of similar units.