The invention discloses a coal gangue power generation and CO2 mineralization cooperative utilization system and a working method thereof, and belongs to the technical field of solid waste resource utilization. Comprising a coal bunker, a coal preparation unit, a boiler unit, a power generation unit, a denitration unit, a dust removal unit, a desulfurization unit, a mineralization unit, a fly ash drying unit, a cooling tower, a chimney and a sewage treatment unit. A coal preparation unit and a sewage treatment unit are improved on the basis of an existing coal gangue blending combustion coal-fired power generation system, a mineralization unit and a fly ash drying unit are added, the system can fix part of CO2 in flue gas through the mineralization process of the mineralization unit, and emission reduction of CO2 is achieved; meanwhile, CaO and MgO in the fly ash can be converted into CaCO3 and MgCO3 in the mineralization process, the application field of the solid waste fly ash is widened, and the utilization rate of the fly ash is increased. According to the invention, the utilization of coal gangue solid wastes and the reduction of CO2 emission can be realized; meanwhile, the content of CaO and MgO in the fly ash can be reduced, and the application of the fly ash in the field of building material manufacturing is improved.