<p>Currently, the specific mechanism by which the three components of biomass act on coal gangue combustion remains unclear, and existing studies lack in-depth exploration of the interaction mechanism at the component level between the two. In this paper, experiments on co-combustion of hemicellulose (HEM) and coal gangue (CG) were carried out to systematically investigate the effects of hemicellulose on the pyrolysis behavior, combustion characteristics, and gas emissions of coal gangue, and to deeply analyze the interaction mechanism between the two fuels during co-combustion. The polysaccharide substances contained in HEM degrade into various volatile products and undergo oxidation reactions, mainly including benzene, alcohols, ethers, NH₃, and phenols. The N-H, C-O, C = C, and O-H bonds in the products were detected. When the mixing ratio of CG to HEM is 1:3, an obvious synergistic effect promoting combustion appears between the fuels in the main combustion stage after 270℃. When the HEM ratio is 75%, the temperature-averaged thermal coupling coefficient of co-combustion is the highest compared with the other two mixing ratios. After 250℃, the influence of interactions on CO₂ emissions showed multiple changes. The research results are helpful to provide a theoretical basis for optimizing the co-combustion technology of coal gangue and biomass.</p> Graphical abstract <p></p>