Abstract: In this paper,an aqueous two-phase system(ATPS)was used in separation of chlorogenic acid from Lonicera japonica leaf and the its antioxidant activity of the chlonogeni acid was studied. Four different ethanol/inorganic salt systems were adapted to extract the chlorogenic acid,and the effects of ethanol concentration,salt content,extract time and extract temperature on the extraction efficiency of chlorogenic acid were discussed in detail. Also,response surface design was employed to evaluate the effect of ethanol concentration,extraction time,NaH₂PO₄ addition and their interactions. The results showed that the aqueous two-phase system(ethanol/NaH₂PO₄)had the best extraction effect. The optimal conditions for chlorogenic acid extraction were that,3.15 g NaH₂PO₄,28.5% ethanol concentration and 49 min extraction time. The chlorogenic acid yield under the optimal conditions was 80.2%. The scavenging ability of the chlorogenic acid reached 84.2% at 0.5 mg/mL against DPPH radical,and the inhibitory effect of lipid peroxidation attained 88% at 1 mg/mL. These results suggested that the aqueous two-phase system(ethanol/NaH₂PO₄)was efficient in extracting chlorogenic acid from Lonicera japonica leaf and had the potential to be used in chlorogenic acid extraction industry.