Abstract: In order to study the effect of the chitin binding protein D (CbpD) on the virulence and related biological characteristics of Vibrio alginolyticus, we constructed the cbpD gene deletion mutant strain of V. alginolyticus ZJ-T by homologous recombination technique. Then we compared the virulence to Danio rerio and other related physiological processes between the wild type strain and the cbpD gene mutant strain, including the growth ability, motility, extracellular protease secretion activity, hemolytic activity and antibiotic sensitivity, biofilm formation, hydrogen peroxide and copper ion resistance as well as ion absorption capacity. The results show that due to the absence of cbpD gene, the swimming motility, swarming motility and extracellular protease activity all reduced, while the resistance to copper ion of the mutant strain strengthened, and its virulence toD. rerio was weakened. However, the deletion of cbpD gene did not affect the growth of the strain in nutrient-rich medium, biofilm formation, hemolytic activity, stress response to H₂O₂, uptake and utilization of iron and sensitivity to most antibiotics. In conclusion, the results indicate that cbpD may promote the virulence by positively regulating the motility, extracellular protease secretion activity of V. alginolyticus.