Steam explosion fish bone was hydrolyzed using five different proteases. Alcalase and Protamex were identified as the optimal hydrolytic enzyme. Fish bone were hydrolyzed by Alcalase （HA） and Protamex （HP） to achieve degrees of hydrolysis（DH） of 5%， 10% and 15%， respectively. The antioxidant activity and relative molecular weight of fish bone hydrolysates were investigated. The results showed that the hydrolysates of the antioxidant activity with a dose-dependent manner. HP with DH 10%（HP10） showed the highest DPPH， ABTS and hydroxyl radical scavenging activity and the IC50 value were 2.85， 0.99 mg/mL and 4.91 mg/mL， respectively. The relative molecular weight was mainly distributed below 500 u， accounting for 75.08%. Whereas HA with DH 15%（HA15） showed the highest reducing power， the absorbance was 0.75 at 700 nm. The relative molecular weight of the hydrolysates decreased with the increase of DH. The study provide basic data for the preparation of antioxidant hydrolysates of fish bone.