Three kinds of original coal gangue from different emission places were taken as the research object, and the dry-wet cycle, freeze-thaw cycle and disintegration resistance test were used to accelerate the weathering of coal gangue aggregate, aiming to study the weathering characteristics of coal gangue. The weathering characteristics of coal gangue aggregate were characterized by the mass loss rate and crushing value index after accelerated weathering. The effects of accelerated weathering system, particle size and service state on the weathering characteristics of coal gangue aggregate were studied. At the same time, the weathering mechanism of coal gangue was revealed by XRD, SEM and EDS. The results show that the mass loss rate and crushing value index of coal gangue aggregate obtained by accelerated weathering of dry-wet cycle are closest to coal gangue aggregate weathered for 180 d under natural state. Moreover, the larger the particle size of coal gangue aggregate, the more likely it is to be weathered, and the weathering of coal gangue aggregate is not obvious under service state. The microscopic test results show that the weathering mechanism of coal gangue is that the mineral composition and structure inside the coal gangue are destroyed during the weathering process, resulting in disintegration and shedding, while the coal gangue in the service state can effectively reduce its weathering due to the encapsulation of cementitious materials.