A Reynolds mass flux model is proposed for the simulation of CO2 absorption into aqueous 2-amino-2-methyl-1-propanol (AMP) solutions in a packed column. With the proposed model, distributions of concentration and temperature as well as velocity can be obtained. In the mathematical expression of the proposed model, the modeled Reynolds mass flux equation is used to close the turbulent mass transfer equation so that the generalized Boussinesqs postulation is abandoned. The feature of the closure method is that the anisotropy of turbulent mass diffusion can be characterized. To validate the proposed model, a simulation is carried out for CO2-AMP absorption in a randomly packed column. The simulated results are compared with the experimental data in literature, and satisfactory agreement is found between them. Besides, the anisotropy of turbulent mass diffusion characterized by the proposed model is discussed and found to be consistent with that from experimental correlations. Finally, the simulations reveal that the anisotropic turbulent mass diffusion plays a significant role in the concentration distribution in a packed column.