Process of CO2 absorption by monoethanolamine (MEA) solutions was conducted in microchannel reactors and effects of several parameters on the absorption process were evaluated and analyzed, i.e., MEA concentration, temperature, pressure, molar ratio of MEA to CO2 and aspect ratio of microchannel. Based on the process characteristics of CO2 absorption in microchannel, a method was proposed to determine the reaction rate constant between CO2 and MEA under ambient pressure and an Arrhenius-type equation was established for the constant over temperature range from 25 degrees C to 45 degrees C. The corresponding activation energy was found to be 22.2 kJ/mol while the pre-exponential factor was equal to 1.09 x 10(9) L/(mol s). The equation is reliable and convenient to the design and simulation of CO2 absorption process in microchannel. (C) 2013 Elsevier B.V. All rights reserved.