The disclosure discloses an alginate lyase and application thereof, and belongs to the technical field of biology. The alginate lyase provided by the disclosure has high degradation activity, and the enzyme activity reaches 65 U/mg; the alginate lyase is stable in nature, and the enzyme activity remains 98% or higher of the initial enzyme activity after storage at 4° C. for 18 months; and the alginate lyase has high product specificity. The disclosure uses E. coli as a host to express the alginate lyase derived from V. natriegens, the obtained recombinant E. coli can produce the alginate lyase secreted extracellularly in a conventional LB medium without adding an induction substrate sodium alginate, so the downstream processing technology of protein is simplified, and the disclosure has great industrial application potential.