Abstract: The total rate of mass transfer for the case of non-equilibrium at the liquid liquid interface for a non-ideal laminar jet was derived as follows. The interfacial mass transfer coefficient ks was then calculated from the experimental . The laminar jet was used for studying the interfacial diffusional resistance of the liquid-liquid systems. It was measured that the isobutanol-water system at nominal contact time of 0.065 to 0.342 seconds and temperature of 25℃ had interfacial resistance of 1.4 hours/meter and the ethyl acetatewater system at nominal contact time of 0.066 to 0.262 seconds and three temperatures had interfacial resistances as follows. Temperature, ℃ 20 25 30 Interfacial resistance, hours/meter 2.4 1.6 1.2 The cyclohexanol-water system at nominal contact time of 0.081 to 0.404 seconds and temperature of 25℃ had interfacial resistance of 6.3 hours/meter. From the experimental results, the interfacial resistance is closely related to the temperature, and increases with a decrease in temperature. For ethyl acetate-water system, tap water or aqueous solutions with small amount of surface-active agents such as Nekal BX or sodium hexadecanyl sulfonate was also used as jet liquid to study the interfacial resistance of mass transfer. It was found that these all Had no effect on the rate of mass transfer.