This study was to investigate the preventive effects in anti-oxidation of Ulva lactuca extract fractions (ULEF) against $CCl_4$ toxification in liver total homogenate and mitochondrial fraction of ULEF-pretreated and carbon tetrachloride $(CCl_4)-posttreated$ rats. ULEF was intraperitoneally administered into rats at dose of 1 ml/kg for14 days. On the day 15, 3.3 ml/kg of $CCl_4$ dissolved in olive oil (1:1) was injected 12 hr before anesthetization. Activities of superoxide dismutase(SOD) in mitochondrial fraction were measured and catalase (CAT), glutathione peroxidase (GPx), malondialdehyde (MDA) in liver total homogenate. SOD, CAI and GPx were higher in the ULEF-pretreated and $CCl_4-posttreated$ group than those in the $CCl_4-posttreated$ group, and the pretreatment of ULEF decreased MDA. These results showed that the pretreatment of ULEF had the preventive role in the activities of anti-oxidative enzymes, SOD, CAT and GPx