A solid amine adsorbent was prepared by modifying a porous polystyrene resin (XAD-4) with chloroacetyl chloride through a Friedel–Crafts acylation reaction, followed by aminating with tetraethylenepentamine (TEPA). The adsorption behavior of CO2 from a simulated flue gas on the solid amine adsorbent was evaluated. Factors that could determine the CO2 adsorption performance of the adsorbents such as amine species, adsorption temperature, and moisture were investigated. The experimental results showed that the solid amine adsorbent modified with TEPA (XAD-4-TEPA), which had a longer chain, showed an amine efficiency superior to the other two amine species with shorter chains. The CO2 adsorption capacity decreased obviously as the temperature increased because the reaction between CO2 and amine groups was an exothermic reaction, and its adsorption amount reached 1.7 mmol/g at 10 °C in dry conditions. The existence of water could significantly increase the CO2 adsorption amount of the adsorbent by promoting the chemical adsorption of CO2 on XAD-4-TEPA. The adsorbent kept almost the same adsorption amount after 10 cycles of adsorption–desorption. All of these results indicated that amine-functionalized XAD-4 resin was a promising CO2 adsorbent. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45046.