In order to develop and utilize the by-product mucus of loach processing and circulation， a kind of Paramisgurnus dabryanus mucus polysaccharide (PDMP) was extracted from the mucus of Paramisgurnus dabryanus by ultrasonic-assisted water extraction and alcohol precipitation method. The chemical composition of PDMP was analyzed by UV spectrum， gel filtration chromatography， high performance liquid chromatography， Fourier transform infrared spectroscopy， 1H NMR and 13C NMR. The physicochemical properties of PDMP were studied by X-ray diffraction， thermogravimetric analysis and scanning electron microscopy. The results showed that the total sugar content of PDMP was (95.51±2.27)%， and the sulfate content was (23.41±0.87)%. PDMP did not contain uronic acid and contained acetyl group. The molecular weight of PDMP was 362 928 u. PDMP was composed of fucose， galactose， mannose， glucose and xylose with a molar ratio of 13.27 ∶ 5.68 ∶ 2.31 ∶ 2.23 ∶ 0.45. PDMP contains (1→) -and (1→6) -α-glycosylation and β-glycosylation pyranose. PDMP had strong thermal stability and certain crystallinity， with uniform dense honeycomb holes on the surface and different sizes of holes inside. In addition， in vitro hypoglycemic studies showed that the IC50 values of PDMP on α-amylase and α-glucosidase inhibitory activities were 152 μg/mL and 550 μg/mL， respectively. 9 mg/mL PDMP inhibited α-amylase and α-glucosidase activities by 65.02% and 86.40%， respectively. The results of this study deepened the understanding of loach mucus and provided a theoretical basis for the application of PDMP in modern food industry and medicine.