Abstract: The extraction equilibrium characteristics of amine solution systems have been studied. D2EHPA(in kerosene) is selected as a solvent to separate amines from dilute solution. The effects of pKa of amines, complexing agent concentration, and pH of solutions are discussed. An expression of equilibrium distribution that includes chemical complexation and physical dissolution simultaneously has been proposed. With the FT-IR spectroscopy, mechanism on of amines with D2EHPA is investigated.