Abstract: Resin-based spherical activated carbon (RSAC) with high specific surface area and large mesopore volume (HRSAC) was prepared from spherical solid waste ion exchange resin by CO₂ activation and acid treatment, and HRSAC supported polyethyleneimine (PEI-HRSAC) adsorption materials were prepared. The effects of PEI loading and adsorption temperature on CO₂ adsorption performance were systematically investigated. The results indicate that the optimal activation conditions are the activation temperature of 950 °C and activation time of 1 h. Subsequently, the as-prepared RSAC is treated with hydrochloric acid, and the obtained supported HRSAC has a specific surface area of 1365 m²/g. The mesopore volume of 2.04 cm³/g, and the mesopore diameter is mainly distributed in the range of 10—40 nm. The CO₂ adsorption performance of PEI-HRSAC adsorption materials increases firstly and then decreases with the increasing of adsorption temperature and PEI loading, respectively. When the PEI loading is 65% and the adsorption temperature is 75 °C, the CO₂ adsorption capacity of the obtained adsorption materials reaches the maximum value of 4.09 mmol/g, and remains at a high level (3.66 mmol/g) after 4 cycles of adsorption and desorption.