Abstract: Proteases from sea cucumber (Stichopus japonicus) viscera have been studied.Casein digestion assay revealed acidic proteases with optimum activity at pH2.0 and pH 5.0, and alkaline proteases with optimal activity at pH8.0 and 12.0, respectively.Sea cucumber visceral protein were hydrolyzed by endogenous proteases alone or one of eight different exogenous proteases (flavourzyme, bromelain, papain, neutral protease, alkaline protease, trypsin, acid protease and pepsin) to produce the antioxidative hydrolysates.Bromelain has shown efficient hydrolysis for sea cucumber visceral protein to obtain the hydrolysates possessing the highest radical scavenging activity, and its optimum hydrolysis conditions were determined by orthogonal experimental design method as follows: pH value 7.8, temperature 35℃, dosage of enzyme 5.0g /100g, and time 1h, under which the scavenging rate of hydroxyl radical and superoxide anion radical were 79.15% and 28.57%, respectively.