In this paper, 3-methylaminopropylamine (MAPA) and diethylaminoethanol (DEEA) were mixed in certain ratios, and a novel 3-methylaminopropylamine (MAPA)/diethylaminoethanol (DEEA) composite organic amine sorbent was investigated for CO2 absorption and desorption. By controlling different solvent ratios and experimental temperatures, the absorption and desorption experiments were carried out under different concentration ratios and temperatures, and the optimal CO2 capture performance of the new composite organic amine absorbent was investigated under different conditions. The experimental results showed that when the solvent ratio of the new composite organic amine absorber was MAPA:DEEA=10 wt%:20 wt%, and the absorption temperature was kept at 308.15 K, the CO2 absorption of the new composite organic amine absorber was as high as 0.97 mol CO2/mol amine, and the CO2 desorption of the new composite organic amine absorber was investigated next. Next, the CO2 desorption effect of this new composite organic amine absorber was investigated. It was found that when the desorption temperature was 90℃, the desorption rate of the absorbent rich liquid was as high as 77.74%, at this time, the absorbent did not reach the boiling point, so as to avoid the loss of absorbent due to the evaporation of the absorbent by thermal boiling. The MAPA/DEEA absorption system was analyzed by NMR spectroscopy, and the reaction principle of the absorbent and CO2 was deduced: MAPA first reacted with CO2 to generate an amphoteric intermediate product. Then DEEA deprotonates the product to form carbamate, and MAPA can promote the reaction rate of the composite absorber with CO2, while DEEA can act as a proton acceptor to enhance the CO2 absorption capacity of MAPA.