Squid head protein was hydrolyzed with a commercial protease,Flavourzyme 500MG in the present study. Changes in the degree of hydrolysis( DH) from different hydrolysates were determined and investigated to find out their relationships with antioxidant activities. Results showed that in the range of 0 ~ 39. 80%( DH),the levels of polypeptides and total free amino acids increased with the increase of the degree of hydrolysis. Moreover,the antioxidant activities including superoxide radical scavenging capacity,DPPH radical scavenging capacity,hydroxyl radical scavenging capacity,reducing power,antioxidant value,and Ferrous iron chelating of the hydrolysates increased with the higher degree of hydrolysis. When the degree of hydrolysis was at 39. 80%,the hydrolysates exhibited the strongest antioxidant activities with high amount of polypeptides and total free amino acids( 12. 97 mg / mL and 4. 49 mg / mL). At that level of hydrolysis degree,the antioxidant measurements were analyzed to be 40. 04%,32. 72%, 45. 4%,1. 449,0. 697 mg / mL and 43. 34%,respectively. These results demonstrated that squid head protein hydrolysates had high antioxidant activity and thus had important application value.