Abstract: Small amounts of CO₂ impurities contained in natural gas affect the efficiency of chemical looping methane decomposition for hydrogen production. 8-16 mesh coconut shell activated carbon (AC) was used as a multifunctional carrier, and the effect of 0-7.2% CO₂ on methane decomposition efficiency was studied at temperatures of 850, 900℃ and 950℃. The results show that CO₂ at different concentrations could improve the decomposition efficiency of methane, among which the 4.8% CO₂ concentration was the most favorable. Further studies on the mechanism of CO₂ in promoting the efficiency of methane decomposition revealed that positive impact of CO₂ was mainly manifested in the early stage of AC. Studies also showed that CO₂ was difficult to react with deposited carbon, and its role in deposited carbon elimination was not obvious. Materials Studio software was used to simulate the effect of CO₂ on the adsorption of methane molecules on AC at high temperatures, and the results showed that CO₂ had no significant effect on the adsorption process. Further characterization and analysis showed that although the addition of CO₂ did not change the type of oxygen-containing functional groups, it could effectively increase the concentration of oxygen-containing functional groups, which was beneficial to the increase in active sites, thereby improving the catalytic performance of AC