In order to study the influence of grain size difference on the distribution of gangue components after crushing, taking gangue in mahuangliang coal mine as the research object, the grain size distribution law of gangue after crushing by means of screening, grinding, chemical composition testing and other means, and the change of main chemical composition of gangue under the condition of different width of discharge port and grain size were studied. The results show that the characteristic grain size of gangue grain size distribution model has a logarithmic increasing trend and the uniformity index has an exponential decreasing trend with the increase of the drainage port width. The composition of gangue with different grain sizes also changes with the grain size. With the increase of the width of the discharge port, the distribution rate of each component is affected to different degrees. Gangue particles containing CaO and MgO are enriched in coarse-grained products. The particles containing Fe2O3 gradually concentrated from fine to coarse. Particles containing Al2O3, SiO2 and C are more likely to be broken and enriched in fine-grained products. With the increase of gangue particle size, the distribution rate of each component shows a law of first increasing and then decreasing, and the enrichment ratio with the change of particle size conforms to the form of “”.