Collagen from tilapia fish scales was hydrolyzed by three kinds of commercial enzymes (Alcalase, Protease type XIV and Collagenase) for 0, 1, 2, 3, 4 and 5 hours. The antioxidative activites of the hydrolysates were measured by the scavenging effect on α\,α\-diphenyl-β-picrylhydrazyl (DPPH) radical, reducing power and chelating abilities of metal ion Cu2+. Results showed that the highest antioxidative activity was found in 2% Alcalase hydrolysates at 50℃ for 4 hours. Three fractions of the hydrolysate with different molecular weight were separated by using ultrafiltration. Fractions with 5 ~ 10 kDa and < 5 kDa had a higher effect on DPPH scavenging. Reducing power increased with the molecular weight of the fraction; fraction with 5 ~ 10 kDa and <5 kDa also had a higher chelating ability of Cu2+. The hydrolysates of scales collagen possessed antioxidant activity, and the mechanism of antioxidation seemed dependent on the molecular weight of the peptides.