Several parts of Lythrum salicaria were used for this study. Scavenging activities on radicals, inhibitory activity on linoleic acid peroxidation and total phenol contents of extracts from root, flower, and aerial part were evaluated. Flower and root selected from in vitro assay were subjected to in vivo assay on $CCL_4$-induced liver injury rat model for two weeks. Carbon tetrachloride intoxication on rats produced large amounts of hepatic lipid peroxidation product, thiobarbituric acid reactive substance (TBARS) compared with normal rats. Treatment with root extract of L. salicaria (LSR) showed effective inhibitory activity on lipid peroxidation product. Administration with LSR extract significantly alleviated $CCL_4$-induced increase in GPT activity which were more effective than silymarin. The results of this study suggest that root and flower of L. salicaria have antioxidant and liver protecting activities, and root part is the most effective candidate to develop a new functional material.