Accurate identification of influencing factors of fretting fatigue is crucial for its assessment and control. To address the fracture problem of AA2024-T351 alloy under fretting fatigue， this study utilizes a crystal plasticity finite element model that incorporates microstructural sensitivity to investigate the impact of grain gradient representation on fretting fatigue in the AA2024-T351 alloy. Additionally， a submodel approach is employed to calculate the contact region of the fretting fatigue specimens， and the cumulative plastic slip is analyzed to determine the crack initiation location and predict crack initiation life. The study reveals that the grain gradient results in an uneven distribution of stress fields within metallic materials due to variations in grain sizes and grain boundary conditions. Compared to the fretting fatigue contact surface， the grain gradient exhibits a significant change in crack initiation locations in the subsurface. Moreover， the grain gradient evidently affects the crack initiation life of fretting fatigue. The research findings indicate that the distribution of grain gradient alters the plastic deformation characteristics between grains. As the grain gradient increases， the subsurface crack initiation life gradually surpasses that of the contact surface. The variation in grain gradient significantly influences the subsurface crack nucleation locations， thereby determining the tendencies of crack propagation. Building upon these research conclusions， modifying the grain gradient distribution through material processing methods effectively mitigates the crack initiation and propagation of fretting fatigue.