A novel experiment is designed to visually study the interphase mass transfer in an immiscible liquid-liquid system using the planar laser-induced fluorescence method combined with the refractive index matching technique. Rhodamine B is chosen as the fluorescence tracer because it can dissolve in both aqueous and organic phases. The experimental results indicate that the mass transfer equilibrium time is negatively correlated to the agitation speed. For the Rushton disk turbine, the interphase mass transfer efficiency is enhanced as the impeller clearance increases from T/10 to 2T/5. Furthermore, the interphase mass transfer process is dampened and the equilibrium time increases continuously when the volume fraction of NaI solution increases from 2 to 50%. When the impeller eccentricity increases, the mass transfer equilibrium time increases correspondingly and the trend of its change in the immiscible liquid-liquid system is time in the single phase.