Schizochytrium　protein　hydrolysate　(SPH)　was　prepared　through　stepwise　enzymatic　hydrolysis　by　alcalase　and　flavourzyme　sequentially.　The　proportion　of　hydrophobic　amino　acids　of　SPH　was　34.71%.　The　molecular　weight　(MW)　of　SPH　was　principally　concentrated　at　180-3000　Da　(52.29%).　SPH　was　divided　into　two　fractions　by　ultrafiltration:　SPH-I　(MW　＜　3　kDa)　and　SPH-II　(MW　＞　3　kDa).　Besides　showing　lipid　peroxidation　inhibitory　activity　in　vitro,　SPH-I　exhibited　high　DPPH　and　ABTS　radicals　scavenging　activities　with　IC50　of　350　μg/mL　and　17.5　μg/mL,　respectively.　In　addition,　the　antioxidant　activity　of　SPH-I　was　estimated　in　vivo　using　the　model　of　acute　alcohol-induced　liver　injury　in　mice.　For　the　hepatoprotective　effects,　oral　administration　of　SPH-I　at　different　concentrations　(100,　300　mg/kg　BW)　to　the　mice　subjected　to　alcohol　significantly　decreased　serum　alanine　aminotransferase　(ALT)　and　aspartate　aminotransferase　(AST)　activities　and　hepatic　malondialdehyde　(MDA)　level　compared　to　the　untreated　mice.　Besides,　SPH-I　could　effectively　restore　the　hepatic　superoxide　dismutase　(SOD),　catalase　(CAT),　and　glutathione　peroxidase　(GSH-Px)　activities　and　glutathione　(GSH)　level.　Results　suggested　that　SPH　was　rich　in　biopeptides　that　could　be　exploited　as　antioxidant　molecules　against　oxidative　stress　in　human　body.　©　2017　by　the　authors.