A concept that the driving force of gas-liquid interphase mass transfer comes from the interfacial non-equilibrium is proposed in this paper. For the absorption process, based on the general chemical potential driving force equation, the concentration relation between two phases at interface is derived and solved under different conditions as mass transfer occurs, it shows that the interfacial concentration of absorbed component at liquid side is strongly affected by a Biot number Y-0 and is bulk concentration dependent. The CO2 interfacial concentration of liquid side in stationary absorption by pure methanol, ethanol and n-propanol absorbent respectively are measured by the use of micro laser holographic interference technique, the experimental results are in good agreement with the computation. (c) 2005 Elsevier Ltd. All rights reserved.