Abstract: The abundant pore structure and carbon structure make lignite an excellent raw material for the preparation of carbon-based porous materials. In this paper, lignite-based porous materials were prepared by KOH activation, and their adsorption and separation properties for CO2/N2 were tested. The key influencing factors and adsorption mechanism were analyzed. The results show that the samples prepared by pyrolysis at 650 °C with 33% KOH have the best adsorption and separation performance, and their CO2/N2 adsorption capacity reaches 2.358 mmol/g and 1.010 mmol/g at atmospheric pressure. Appropriate increase in system pressure can significantly improve its adsorption and separation performance. At 1.5 MPa, the CO2 adsorption capacity is greatly increased to 29.37 mmol/g. Thermodynamic parameters and Langmuir-Freundlich model fitting results reveal that the adsorption of CO2/N2 by Shengli lignite is mainly physical adsorption. The results of infrared spectroscopy indicated that chemical functional groups did not significantly influence adsorption. It was clear that the catalyst's excellent performance mainly resulted from the unique pore structure created by KOH activation, which was centered around 0.65-0.7 nm micropores. This study clearly reveals the structure-activity relationship between "adsorption performance-KOH ratio-activation temperature-pore structure", which provides a basis for the directional design of high-performance lignite-based carbon adsorption materials.