This study aims to study the enzymatic characterization of extracellular laminarases from Microbulbifer sp. ALW1 and the antioxidant activity of the enzymatic hydrolysates. The results showed that the optimum temperature of laminarinase was 45 ℃ using laminarin as the substrate， and the enzyme activity was stable under 35 ℃. The optimum pH of laminarinase was 5.5， and the enzymatic activity was stable at pH between 6.0 and 8.0. Na+ could promote the enzyme activity， but K+， Fe2+， Cu2+， Co2+， Mn2+， Ba2+， Cd2+ and Zn2+ could inhibit the laminarinase activity to some extent. The enzymatic hydrolysates had reducing ability and scavenging power on ABTS and hydroxyl radicals. The half inhibitory concentration （IC50） values of scavenging activity towards ABTS and hydroxyl radicals were 15.2 mg/mL and 1.7 mg/mL， respectively. These results showed that the enzymatic hydrolysates had antioxidant activity.