Abnormal wear issues of the coupler system exist in heavy-haul trains and are rarely studied before. In this paper, we thoroughly report and investigate the abnormal wear phenomenon of the coupler using theoretical and experimental strategies. Firstly, the operational conditions of the trains with worn couplers are analyzed through field tests. Then, the causes of the coupler abnormal wear are theoretically analyzed according to structural characteristics. Next, A refined dynamic model of coupler considering the coupler components is developed and validated. The key influencing factors of abnormal wear are studied, including the wear depth of the component and the friction coefficient of the follower. Experiments and simulations prove that multiple braking of trains will lead to upward movements of the follower and then induce contact between the follower and the coupler yoke, further resulting in abnormal wear. Finally, countermeasures are proposed to mitigate the abnormal wear of the coupler system.