Sequential extraction method was used to separate the ethanol extract of Abelmoschus manihot (L.) Medic flowers. Four extracts were obtained by different polarity solvents, including petroleum ether, ethyl acetate, n-Butyl and water. The antioxidant properties of the four fractions were evaluated by the reducing power and scavenging activities of three free radicals, namely hydroxyl radical (•OH), superoxide radical (O2-•) and DPPH radical (DPPH•). The extract with strongest antioxidant capacity was investigated by measuring the effects on hemolysis of mice red blood cells, malondialdehyde (MDA) generation in mice liver homogenate and mitochondria and the swelling degree of liver mitochondria. The order of radicals scavenging capacity of the four extracts was found to be DPPH•＞•OH＞O2-•and the ethyl acetate extract (EA) showed the highest radicals scavenging capacity. The EC50 of these free radicals were 3.52，44.96，376.87 μg/mL, respectively. The effect of EA on anti-lipid peroxidation were studied by in vitro system. EA could inhibit the hemolysis of mice red blood cells significantly (p＜0.05) , reduced the generation of MDA in mice liver homogenate and mitochondria in the concentration range of 50~500 μg/mL and alleviated the swelling of liver mitochondria in a dose-dependent manner.