This study explored the absorption of CO2 by the polyethyleneimine (PEI) solution in a rotating packed bed (RPB). In order to boost the CO2 absorption effect, the liquid detention phenomenon in the RPB was utilized to overcome the short residence time of liquid. The effects of different operating parameters on CO2 absorption efficiency (η) and gas-phase volumetric mass transfer coefficient (KGav) in the RPB were investigated. The experimental results indicated that the RPB can greatly intensify the absorption of CO2. η and KGav increased from 3.3 % and 0.041 kmol·m−3·h−1·kPa−1 to 76.0 % and 1.634 kmol·m−3·h−1·kPa−1, respectively, as the rotational speed of the RPB rose from zero to 700 rpm with 250 mL detained liquid. It was also found that the liquid detention phenomenon can significantly elevate η and KGav as a result of extended liquid residence time and increased liquid holdup in the RPB. When the detained liquid volume increased from zero to 250 mL, η and KGav increased by 55.6 % and 113.1 %, respetively. In addition, it was observed that CO2 load in the rich PEI solution increased from 9.650 to 11.189 molCO2/kg PEI while η remained around 85 % after five cycles of absorption–desorption, suggesting an excellent cyclic stability of PEI. This work contributes to the development of viable CO2 capture technologies by intensifying the CO2 absorption process in the RPB with an efficient absorbent.