Shear viscosity of concentrated aqueous solutions of alkylaminoethanols was determined with changing the length of the alkyl chain and the concentration of dissolved CO2. The viscosity increased with increasing the CO2 loading, reflecting the strengthening of the intermolecular electrostatic interaction. The dependence of the viscosity on both temperature and CO2 loading was described by a modified version of Vogel-Fulchar-Tammann equation. Compared at the same volume concentration of CO2, the viscosity increased with increasing the alkyl chain lengths, and the dependence on the alkyl chain length increased with the CO2 loading. At the same time, small-angle X-ray scattering profiles exhibited the presence of a prepeak when the alkyl chain was long, and the prepeak grew with the CO2 loading. It suggests that the presence of the heterogeneous structure increases the shear viscosity of the CO2 absorbents when the alkyl chain is long.