As the waste produced by coal mining and coal washing process, massive piling of coal gangue has a serious negative impact on the ecological environment, and using coal gangue as the aggregate of concrete is in line with the concept of green sustainable development. The loose and porous characteristics of coal gangue aggregate and the feature of showing needle-like or flaky after damage will negatively impact various coal gangue concrete properties. The basic physical and chemical properties of coal gangue aggregate were described briefly, while the effect of coal gangue aggregate on workability, mechanical properties, durability, and interfacial transition zone of concrete was also summarized. To compensate for the various defects of gangue aggregates used in concrete, reinforcement techniques relating to gangue aggregates have been proposed to improve the efficiency of gangue resource utilization. Four modification techniques-surface coating, such as water glass modification, thermal activation, and microbial-induced calcium carbonate precipitation techniques can strengthen coal gangue’s defects as an aggregate. On this basis, a summary of the strengthening mechanism and research progress of the above modification technology, and the future of the gangue aggregate and its modification technology in the concrete research direction were put forward to promote the application and development of coal gangue concrete.