Abstract: Water chestnut peel polyphenols were extracted with different methods，Its ability to remove DPPH free radical was determinated. The water chestnut peel polyphenol antioxidant activity with different extracting methods were determinated by half inhibitory concentration（ IC₅₀ ）. The results show that the water chestunt peel polyphenols from the several different methods have strong antioxidant capability，they are stronger than that of the control. The water chestnut peel polyphenol antioxidant activity is relatively stronger extracted with ethanol—ammonium sulphate aqueous two-phase system of microwave processing ，the extracting conditions are ：ethanol-water ratio 0. 5 ，（NH₄）₂SO₄ dosage 0. 30g/mL，microwave power 288 W，extracting time 8 min，under these conditions，it can obtain stable aqueous two-phase system and high water chestnut peel polyphenol content.

Key words: water chestnut peel polyphenols, aqueous two- phase system, DPPH free radical, antioxidant activity