OBJECTIVE：To estab lish the fingerprint ，analyze the monosaccharide composition and content ，investigate the inhibitory effects of the polysaccharide from Desmodium styracifolium on α-glucosidase in vitro . METHODS ：Polysaccharide from D. styracifolium was prepared by water extraction and ethanol precipitation. After hydrolyzed by TFA and derived by PMP ，HPLC method was adopted to establish the fingerprint （using glucose peak as reference ），and analyze the constituent and content of monosaccharide. The content determination was performed on Phenomenex Luna C 18 column with mobile phase consisted of acetonitrile-0.05 mol/L potassium phosphate （pH adjusted to 6.8 with sodium hydroxide ）in gradient elution at the flow rate of 0.8 mL/min. The detection wavelength was set at 250 nm，and column temperature was set at 30 ℃. The sample size was 10 μL. Using acarbose as control ，PNPG assay was used to investigate the α-glucosidase inhibitory activity of polysaccharide from D. styracifolium. RESULTS ：There were 9 common peaks in HPLC fingerprints of 18 batches of samples ，and the similarity of 15 batches of samples was higher than 0.90. Totally 7 peaks were identified as mannose ，rhamnose，galacturonic acid ，glucose， galactose，xylose and arabinose. The contents of rhamnose ，galacturonic acid ，glucose，galactose and arabinose were 0.471-2.092， 1.379-8.919，2.560-35.679，1.194-6.905，0.566-4.158 mg/g，respectively. Based on rhamnose ，the molar ratios of the other four monosaccharides were 1.58-4.07，2.26-19.95，2.20-4.21 and 1.31-2.86，respectively. The inhibitory activity of polysaccharide from D. styracifolium on α-glucosidase increased with the increase of dose ，and the half inhibitory concentrations of it was 0.70 mg/mL， lower than 7.76 mg/mL of acarbose （positive control ）. CONCLUSIONS ：Glucose is the main component of D. styracifolium polysaccharide in different batches ，and the contents of monosaccharides are different. The polysaccharide from D. styracifolium have significant inhibitory activity on α-glucosidase，which is better than that of acarbose.