Abstract: Tilapia scraps were hydrolyzed by neutral protease and flavourzyme, and the hydrolysate was fractionated through ultrafiltration membranes with a range of molecular weight cutoffs(MWCO)of 10 ku, to yield the fraction EH10K with MW distribution<10 ku.The zinc chelating salts(CH-0)was produced by EH10K chelating with ZnSO₄.CH-Ⅰ and CH-Ⅱ were the purified components from CH-0 by using 95% ethanol and dialysis(FW=500 u)respectively.The formation of Zn²⁺ chelating salts of hydrolysate was confirmed by the UV-VIS spectra.The physicochemical properties of CH-0, CH-Ⅰ and CH-Ⅱ were analysed and their free radical scavenging activities were evaluated also.The results showed that CH-0 contained 71.86% of protein(on dry basis), 16.08% of Zn, CH-Ⅰ and CH-Ⅱ were 75.94% and 14.49%, 78.83% and 12.20% respectively.The gel chromatography results showed that CH-Ⅰand CH-Ⅱ had three same main absorption peaks compared to CH-0 but had little impurity peaks.The contents of Asp, Glu, Gly, Lys, Arg and His in CH-Ⅱ were high than those of CH-Ⅰ, and all were high than those of CH-0.The content of essential amino acid and branched chain amino acid in CH-Ⅱ were high than that in CH-Ⅰ.CH-0, CH-Ⅰ and CH-Ⅱ showed evident radical scavenging activity in a dose-dependent manner with the IC₅₀ values for hydroxyl radical and 1, 1-diphenyl-2-pycrylhydrazyl(DPPH)radical being 9.08 and 6.07, 8.27 and 3.76, 6.90 and 3.27 mg/mL respectively.The superoxide radical scavenging activity of EH10K was 69.27% at 10.00 mg/mL, CH-0, CH-Ⅰ and CH-Ⅱ showed no effect on superoxide radical scavenging but to promote the oxidation.