The mass transfer in CO2 absorption can be intensified in miniaturized devices. In this paper, the weak CO2 absorption in aqueous glycerol solutions in a serpentine minichannel is studied, with Fourier number Fo < 0.1. The effects of operating conditions on the volumetric mass transfer coefficient k(L)a during the absorption are investigated, and k(L)a ranges between 0.1 and 0.4. k(L)a increases with the increase in the gas and liquid flow rates. Under the influence of the secondary flow, the liquid in the slug enters into the liquid film, intensifies the mass transfer around the main body of the bubble, and causes the asymmetric reduction of the inner diameter of the bubble. The relationship between the bubble shrinkage rate f and the residence time t is explored, and the relationship between the bubble maximum absorption rate f(abs), k(L)a, and variables is obtained. The prediction formula of k(L)a is obtained.