Abstract: The present disclosure provides a Pseudoalteromonas agarivorans strain and a preparation method of an exopolysaccharide (EPS), and relates to the technical field of functional bacteria. In the present disclosure, the Pseudoalteromonas agarivorans strain HJWL2022 has a deposit number of CGMCC No. 26272. Fermentation, centrifugation, alcohol precipitation, protein removal, purification, and drying are conducted with the strain HJWL2022 to obtain a pure EPS. A proportion of a monosaccharide component in the product EPS is controlled by precisely controlling a pH value in a fermentation environment of the strain HJWL2022. Targeted control of a monosaccharide ratio is achieved to enhance a certain biological activity by adjusting fermentation conditions to change a composition of a bacterial EPS.