Abstract: Alginate lyase, as a tool enzyme that can efficiently degrade alginate, plays a significant role in the industrial production of alginate oligosaccharides. In this study, using sodium alginate as the sole carbon source, a bacterial strain with high sodium alginate degradation efficiency was screened and purified from rotten Ecklonia maxima. Based on its morphological, physiological, biochemical characteristics, and 16S rRNA gene sequencing results, the strain was identified as Klebsiella pneumoniae and named SW06. By optimizing the enzyme production and enzymatic hydrolysis conditions, the enzyme activity of the strain was significantly improved. The optimal medium composition for strain SW06 was: sodium alginate 5 g/L, (NH₄)₂SO₄ 5 g/L, MgSO₄·7H₂O 6 mmol/L, NaCl 120 mmol/L, K₂HPO₄ 15 mmol/L, and FeSO₄·7H₂O 0.04 mmol/L. The optimized culture conditions were: 1% inoculum, 90 mL medium volume (in a 250 mL conical flask), agitation speed 180 r/min, and initial medium pH6.0. After optimization, the maximum enzyme activity of alginate lyase reached 311 U/mL, representing a 395% increase compared to the pre-optimization level. Enzymatic property experiments revealed that the optimal temperature for enzymatic hydrolysis was 40 ℃, and the enzyme remained stable within the pH range of 6.0-9.0. The addition of β-mercaptoethanol and NaCl significantly enhanced enzyme activity (≥50% increase). Analysis of enzymatic hydrolysis products indicated that the main products were alginate disaccharide, trisaccharide, and tetrasaccharide. This study successfully screened a bacterial strain with high enzyme activity from Ecklonia maxima, demonstrating potential application prospects and providing a new option for the industrial production of alginate oligosaccharides.