The improper disposal of coal gasification fly ash (CGFA) and coal gangue (CG) is highly susceptible to environmental pollution. Preheating combustion is a proven technology for the efficient combustion of solid fuels. On the basis of this technology and combining the complementary physical properties of CGFA and CG, the synergistic combustion of these two typical solid wastes is expected to occur. In this study, the preheating modification and co-combustion characteristics of CGFA and CG with different blending ratios were investigated. The evolution of the physicochemical structure of the activated char was analyzed via a particle size analyzer, scanning electron microscope, N