The exploration and development of deep coal seam gas up to 3000 m is still in the initial stage, and the gas content and adsorption characteristics of deep coal seam gas are unclear. The adsorption characteristics of deep coal seam gas were obtained through gas content, adsorption capacity and reservoir temperature correction to further deepen the understanding of deep coal seam gas. The isothermal adsorption experiment is carried out with core samples from well X in Block Y, Sulige, 3491–3556 m. The research shows that the gas content of Benxi formation in Sulige main coal seam gas is higher than that of Shanxi formation, and the adsorption capacity is very different, showing longitudinal heterogeneity. Ash content and gas content showed a good linear relationship, the higher the ash content, the smaller the adsorption capacity. And the empirical formulas of adsorption capacity and ash content after correction were obtained. The content of free gas in Benxi formation of deep coal seam gas in Sulige Y block is about 34.77%. The output of gas well will produce free gas first, then free gas and analytic gas. The research results will provide a scientific basis for the calculation of coal seam gas adsorption properties, gas content and resources of Sulige deep coal seam gas.