This study was conducted to investigate the effect of soy protein hydrolyzate on lipid metabolism and antioxidant activity in the rat. Thirty-eight male rats of Sprague-Dawley strain were divided into five groups: casein, isolated soy protein (ISP), seoritae protein hydrolyzate (SH), soluble soy protein hydrolyzate (SS), and insoluble soy protein hydrolyzate (IS). The control diet (casein group) contained 20% casein protein and experimental diet contained 10% casein and 10% isolated soy-protein or soy-protein hydrolyzate. Fecal lipid content was increased and lipid apparent absorption rate was decreased significantly by the ISP group at the first week of experimental period. Blood triglyceride, total cholesterol, LDL-cholesterol and atherogenic index (AI) were decreased by soy protein hydrolyzate groups than casein group. Liver total lipid, triglyceride and cholesterol were not different among groups, but showed decreasing tendencies in soyprotein hydrolyzate groups. The lipid lowering effect was prominent in the IS group among soy protein hydrolyzate groups. Total antioxidant activity showed increasing tendency in the seoritae hydrolyzate group. Liver superoxide dismutase (SOD), glutathione peroxidase (GPx) and catalase activities also showed higher tendencies in the seoritae hydrolyzate group than other groups. In conclusion, insoluble soyprotein hydrolyzate was more effective in lowering body lipids and seoritae hydrolyzate had higher antioxidant capacity among soy protein hydrolyzates.