The optimal conditions for activating coal fly ash (400 ℃, m(NaOH) ∶ m(coal fly ash) = 1 ∶ 2) were obtained by exploring the alkali fusion activation conditions, and the coal fly ash-based zeolite X with the highest relative crystallinity was obtained by hydrothermal synthesis at 80 ℃ for 18 h. The physical characteristics of synthesized zeolite X were characterized by XRD, FT-IR, SEM, and BET. The results show that the synthesized zeolite obtains a relatively specific surface area of up to 315. 6 m2 / g, an average pore diameter of 8. 53 nm, and a total pore volume of 0. 412 cm3 / g. Coal fly ash-based zeolite X also shows higher adsorption capacity of o-xylene, carbon dioxide and hydrogen, which are 75. 20 mg / g, 2. 45 mmol / g, and 0. 22% (mass fraction), respectively. The adsorption behavior can be well fitted by Langmuir adsorption isotherm, which belongs to monolayer adsorption. This study reduces the energy consumption in the zeolite process of coal fly ash, and the prepared coal fly ash-based zeolite X has potential commercial value in energy and environmental protection.