Alginate lyase digestion is an efficient way to degrade alginate into oligosaccharides, which are useful in various areas including chemistry, pharmacy and food industry. Here we determined the sequence of Vibrio sp. QY102 sourced alginate lyase, and set up its heterologous expression in E. coll. We improved its secretion efficiency by replacing the original secretive sequence by E. coil specific signal peptide ompA. We successfully purified the full-length protein in shake flask culture, however, degradation happened during fed batch cultivation. By domain and disorder examination, we found that the protein was completely functional by expressing the C terminal fragment alone. For the final strain we constructed (HMS-ompA-CF), the extracellular enzyme activity reached 375 U/ml in shake flask and 1789 U/ml in fed batch cultivation (5 L bioreactor). And the final protein yield reached 0.58 g/L in fed batch cultivation. We determined that the optimal pH and temperature for the shortened alginate lyase were 7.0 and 39 degrees C, respectively.