Abstract: In order to exploit the active constituents of Macropanax rosthornii,this paper optimized the parameters(solvents,volume fraction of ethanol,the ratio of material to liquid,extraction temperature and extraction time)which influence the yield of the total polyphenol content. Meanwhile,the antioxidant activity of polyphenols in vitro was studied by using the DPPH and hydroxyl radical scavenging rate as indicators. The results showed that the optimum parameters for polyphenol extraction from Macropanax rosthornii were ethanol volume fraction of 50%,solid to liquid ratio of 1∶40 (g/mL),extraction time of 50 min and extraction temperature of 45 ℃,under which the extracted polyphenol content was(0.320±0.02) mEq GA/g. The results of the antioxidant activity showed that the polyphenols from Macropanax rosthornii presented good scavenging rate on DPPH and hydroxyl radicals,with its concentration of decrease 50% free radicals(EC₅₀)of 43.4 μg/mLand 37.6 μg/mL,respectively. Macropanax rosthornii indicates favourable antioxidant activity in vitro,and it deserves to exploit as a potential antioxidant.