Abstract: According to solubilization of surfactant micelle and phase-separation of nonionic surfactant aqueous system induced by temperature, extraction of phenol with Triton X-100 two-phase micellar system was carried out. The results indicated that specific solubilization of phenol in the surfactant-rich phase was directly proportional to its concentration in the aqueous phase. The proportional coefficient (the equilibrium constant) was determined. On the basis of experiments, a model was proposed, which predicated extraction yield as a function of surfactant concentration, solute concentration and pH of system. It also explained that back-extraction of phenol from surfactant-rich phase to aqueous phase by adjusting the pH of system resulted from the change of proportional coefficient by ionization of phenol.