Amine-skeleton solid-amine materials are promising adsorbents for CO2 capture from flue gas. Here, a novel solid-amine microsphere was synthesized by cross-linking the skeleton poly(ethylenimine) (PEI) with ethylene glycol diglycidyl ether in a facile one-pot W/O emulsion system. The material had a remarkable CO2 adsorption capacity of 7.28 mmol/g in the presence of moisture at 20 degrees C, 0.1 bar. The highest ratio of breakthrough capacity to saturation capacity was ca. 84%. According to kinetic simulation, the Avrami kinetic model could better describe the adsorption process of CO2 under different temperatures, in which the value of R-2 was above 0.99 and n was between 1 and 2, indicating that both physical and chemical adsorption mechanisms were performed during adsorption. Moreover, the material had a high swelling speed. Equilibrium was established within 30 s, and the swelling ratio was 271% at equilibrium. The saturated adsorbent could be easily regenerated with a regeneration efficiency of 94.63% after six cycles. The PEI microsphere appears to be a promising candidate material for CO2 capture from flue gas.