Kinetics of rubidium extraction by 4-tert-butyl-2-(alpha-methylbenzy) phenol (t-BAMBP)/sulfonated kerosene in brine solutions were investigated using the rising single drop technique. Parameters affecting the mass transfer mechanism, including the interfacial area, initial alkalinity of aqueous phase, concentration of rubidium ions and t-BAMBP, and temperature were studied. The results indicated that the process of extraction was controlled by the diffusion process, while the chemical reaction occurred at the interfacial area. Dynamic equation of the extraction system, R-e= 2.901 x 10(-5) [Rb+](1.022)[OH-](1.179)[t-BAMBP](0.991)was obtained by non-linear fitting the experimental data. Moreover, a new mechanism of the rubidium extraction with t-BAMBP/sulfonated kerosene was proposed.