Studies have found that natural antioxidants, which are free-radical scavengers, can reduce the risk of diseases caused by free radicals. This work investigated the antioxidant properties of duck proteins hydrolysates. The free-radical scavenging function of CP-1 (M(r) > 10 kDa), CP-2 (5 kDa < M(r) < 10 kDa) and CP-3 (M(r) < 5 kDa), obtained through ultrafiltration and gel filtration were evaluated. The results showed that the lower molecular weight fraction exhibited a stronger free-radical scavenging ability. The highest free-radical scavenging activity was detected in the fraction of p4 purified from CP-3 using Sephadex G-15 column chromatography. The 50% inhibitory value (IC(50)) of p4 for scavenging radicals of superoxide, hydroxyl and 1,1-diphenyl-2-pycrylhydrazyl (DPPH) were, respectively, 0.97 mg mL(-1), 0.84 mg mL(-1) and 1.84 mg mL(-1). Furthermore, the p4 fraction at a concentration of 10 μg mL(-1) increased cell viability from 84.8% to 94% under antioxidative stress in neuroblastoma SK-N-SH cells.