Objective： The alginate lyase gene from Pseudomonas syringae was cloned and expressed in Escherichia coli BL21（DE3）. After the recombinant alginate lyase was purified， the enzyme and the antioxidant activity of the enzymatic hydrolysates were characterized. These will set up a good foundation for further researches of structure and function of this enzyme. Methods： The alginate lyase gene was amplified by PCR and cloned into pET-28a expression vector. After the recombinant enzyme was purified using affinity chromatography， it was characterized. The antioxidant activities of the enzymatic hydrolysates were analysed by detecting the reducing ability and scavenging power on ABTS+ and hydroxyl radicals. Results： The molecular weight of the recombinant alginate lyase from P. syringae was 40.8 kDa. The recombinant enzyme showed activity towards polymannuronate. The optimal temperature and pH of the enzyme were 30 ℃ and 7.5， respectively， and it was stable at temperature below 50 ℃. In addition to SDS and DTT， the recombinant alginate lyase had good resistance to other detected inhibitors and detergents. The enzymatic hydrolysates had the reducing power. The half inhibitory concentration（IC50） values of scavenging ABTS+ and hydroxyl radicals were 1.56 mg/mL and 0.56 mg/mL， respectively. Conclusion： The enzymatic hydrolysates exhibited the antioxidant activity and had potential as antioxidant products.