OBJECTIVE：To evaluate in vitro antioxidant activities of 4 different polar parts of ethanol extract from Amomum tsao-ko，and to lay a foundation for the research and development of antioxidant chemical components in the plant. METHODS ： The dried fruits of A. tsao-ko were crushed ，then were hearted and reflux extracted with 95％ ethanol. The extraction fluid was concentrated by rotary evaporation and evaporated in water bath to obtain the ethanol extract. The extract was dispersed in water ， and then extracted with petroleum ether ，ethyl acetate and n-butanol organic solvents one by one. Each solvent extract was combined and the lower water phase were collected. Finally ，the petroleum ether part ，ethyl acetate part ，n-butanol part and water part were obtained，after rotary evaporation concentration and water bath evaporation. Through in vitro antioxidant activity tests ，using 2， 6-di-tert-butyl-4-methylphenol（BHT）as positive control ，DPPH radical ，superoxide anion radical scavenging ability and Fe 3+ reducing ability of different polar parts of ethanol extract from A. tsao-ko were investigated. RESULTS ：The scavenging rates of 4 polar parts of ethanol extract from A. tsao-ko on DPPH radical were all over 80％；the order of scavenging ability was ethyl acetate part＞BHT＞n-butanol part ＞petroleum ether part ＞water part. Those of the 4 polar parts to superoxide anion radical were between about 30％-40％ mostly；the order of scavenging ability was n-butanol part ＞petroleum ether part ＞water part ＞ethyl acetate part ＞ BHT；but those were weaker than their scavenging ability to DPPH r adical. The polar parts of ethanol extract also had a certain reduction ability to Fe 3+；the order of the reduction ability was n-butanol part ＞BHT＞ethyl acetate part ＞petroleum ether part ＞ water part on the whole ，but that of water part rose to the stron- gest when its concentration was 4.0 μg/mL. CONCLUSIONS： The different polar parts of ethanol extract from A. tsao-kom have certain in vitro antioxidant capacity ，but the order of antioxidant activity of different polar parts was not the same in different antioxidant activity tests ；ethyl acetate part has the 163.com strongest scave nging effect on DPPH radical ，n-butanol part has the strongest scavenging ability on superoxide anion radical and reducing ability on Fe 3+.