In the current research,acid soluble collagen(ASC)from skipjack tuna(Katsuwonus pelamis)fishbone was successfully isolated with the yield of 2.47%(dry weight basis).The antioxidant hydrolysate of ASC(TFCH)was prepared through a two-stage in vitro digestion(3-h pepsin followed by 3-h trypsin),and one new antioxidant peptide(TFCH-P2)was further isolated from TFCH using ultrafiltration,gel chromatography,and RP-HPLC.The amino acid sequence of TFCH-P2 was identified as Gly-Pro-Ala-Gly-Pro-Ala-Gly-Glu-Gln-Gly(GPAGPAGQEG)with molecular weight of 839.87 u([M+H]⁺ 840.68 u).TFCH-P2 exhibited good scavenging activity on DPPH radical,hydroxyl radical,ABTS radical and superoxide anion radical with EC₅₀ of 0.18,0.97,0.52 and 0.38 mg/mL,respectively.TFCH-P2 was also effectively against lipid peroxidation in a linoleic acid model system.The antioxidant activity of TFCH-P2 was due to the presence of hydrophobic amino acid residues within the peptide sequence.The result suggested that TFCH-P2 could be used as natural antioxidant in enhancing antioxidant properties of functional foods and in preventing oxidation reactions in food processing.