The mass transfer characteristics of CO2 absorption into aqueous solution of ionic liquid in microchannel was investigated experimentally by a high speed camera. The influences of the ratio of gas and liquid flow rates (Q(G)/Q(L)) and the concentration of ionic liquid on the liquid side volumetric mass transfer coefficient (k(L)a), liquid side mass transfer coefficient (k(L)) and length of mass transfer zone (L-M) were studied systematically. The results show that both k(L)a and k(L) increase but L-M decreases with the increasing Q(G)/Q(L) and the concentration of ionic liquid. Taking the enhancement of 1-butyl-3-methylimidazolium tetrafluoroborate (Ibmim][BF4]) on the mass transfer into account, a dimensionless correlation for predicting k(L)a was proposed. This work is conducive to the design, optimization and the application of the microchannel reactor for CO2 capture and removal. (C) 2018 Elsevier Ltd. All rights reserved.