<p>Selenopolysaccharides are important class of organic compounds with both selenium and polysaccharide bioactivities, which are more easily absorbed and utilized by the body. In this study, selenized mucus polysaccharide (Se-PDMP) was first synthesized by HNO₃-Na₂SeO₃ method by using <i>Paramecium dabryanus</i> mucus polysaccharide (PDMP) as the experimental raw material, and its physicochemical properties, structural characteristics, as well as inhibitory activities against α-amylase and α-glucosidase were systematically investigated. Key findings are as follows: The selenium content of Se-PDMP reaches 460.10&#xa0;µg/g, indicating the successful introduction of selenium; structural analysis reveals that selenization enhances the intra/intermolecular interactions of polysaccharide molecules, leading to a more pronounced aggregation effect. In addition, in vitro hypoglycemic studies show that Se-PDMP exerts competitive and reversible inhibitory effects on both enzymes, and its inhibitory activity is significantly superior to that of PDMP. These results reveal the potential of Se-PDMP as a novel dual-target (α-amylase/α-glucosidase) inhibitor. This study not only provides new insights into the structure-activity relationship of selenopolysaccharides but also lays an important theoretical foundation for the development of safe and efficient natural-derived agents for the prevention and alleviation of diabetes.</p>