Water extraction and alc?OHol precipitation method was used to extract polysaccharides from Forsythia suspensa, and Forsythia suspensa polysaccharide nano selenium (FP-SeNPs) was prepared through nitric acid-sodium selenite method. UV-Vis, FTIR, XRD, and SEM were used to characterize their absorption spectra, tissue structure, and surface morphology. ?DPPH radical, ?OH radical, and ?ABTS radical were used to investigate the antioxidant capacity of FP-SeNPs in vitro. The hypoglycemic activity of FP-SeNPs was investigated by α-amylase and α-glucosidase inhibition assay. The results showed that the selenium content in FP-SeNPs was 908mg/kg; FP-SeNPs formed a surface structure with granular distribution, changing the surface morphology of polysaccharides, but did not destroy the basic structure of polysaccharides. A new absorption peak was generated at around 270 nm, and a diffuse peak was observed in the XRD pattern between 20°and 30°, which indicated that there was an interaction between FP and SeNPs, and the FP-SeNPs complex was formed. The scavenging ability of FP-SeNPs on ?DPPH, ?OH, and ?ABTS radicals and the inhibitory ability on α-amylase α-glucosidase were concentration-dependent. The scavenging rates of 1.6 mg/mL FP-SeNPs solution on ?DPPH, ?OH, and ?ABTS free radicals were 91.98%, 56.81%, and 87.44%, and the inhibitory rates on α-amylase and α-glucosidase were 55.61% and 72.73%, respectively, which were significantly higher than that of FP (P<0.05).