Ths paper focuses on me mechanism of interfacial mass transfer of a single bubble. based on chemi cal potential driving force, an approach for calculating interracial concentration in practical process is proposed. The absorption proc esses of bubble under bom quiescent an d mobile conditions ale analyzed and discussed respectively. For a staftonary absorption. only in me case of liquid bulk concentration near saturated value. Me tefacial concentration could close to me equilibrium value：For a moving bubble, under ordinary operating condi. Tion (y0>1), me interfacial concentration is far from its equilibrium. Only under bulk concentration near saturated value or a smaller Yo (Yo<0.1) which may involve me complication of additional resistance at interface induced surface contamination or sufactant added. me interfacial concentration could be approximate to equilibrium value. The interfacial concentration close to me interface on liquid side for a single CO, bubble absorbed by methanol measured using a modern optical instrumentation in which me laser holographic interference memOd is adopted wim a real-time and amplification technique. Experimental results show mat me interfacial concentration decreases significan tly with increasing Re an d is far from the eq uilibrium one in a larger Re ran ge. Experiments validate proposed mode1.