With the crude saponin(40.2%) extracted from tea cake as raw material.An aqueous two-phase system based on propyl alcohol/ammonium sulfate was used in separation and purification of saponin.The influences of such factors as the concentration of ammonium sulfate,the concentration of propyl alcoho,temperature and pH were investigated.The results show that, the process separate very speed,product extration ratio and content is high.They were listed as follow:ammonium sulfate concentration 20%,propyl alcoho concentration 23%,temperature 40℃ and pH 7 adjustment.Under the optimal conditions,the extration ratio and the content reached 89.32% and 78.12%.