Abstract: Sweet corn cob polysaccharide is a water-soluble polysaccharide, but its molecular weight is large, and it is difficult to absorb and utilize. Sweet corn cob polysaccharide nano emulsion was prepared by spontaneous emulsification method. Pseudo-ternary phase diagram was used to screen and compare the effects of mixed surfactants with different mass fractions and sweet corn cob polysaccharide solution on the transparency and particle size of sweet corn cob polysaccharide nano emulsion. The optimal formula was obtained, and its in vitro release effect and in vitro hypoglycemic effect were studied. The results showed that, the prepared sweet corn cob polysaccharide nano emulsion is a kind of W/O (water-in-oil) nano emulsion, and the optimal formula was (Tween80:Span80=1:1)/ethanol/liquid paraffin/1.5% sweet corn cobs polysaccharide aqueous solution=33.3%/11.1%/44.5%/11.1%, particle size (43.22±4.84) nm. Polydispersity index（PDI）was (0.320±0.014), pH was (7.6±0.2), the viscosity was (209.9±4.1) cP. The transparency was 97.62%±0.39%. The polysaccharide content was 2.154±0.024 mg/mL. Stability experiments showed that it had good stability. In vitro simulated gastrointestinal fluid digestion experiments showed that sweet corncob polysaccharide nano emulsion had sustained release properties and could prolong the action time. The hypoglycemic experiment in vitro showed that sweet corn cob polysaccharide nano emulsion had a certain inhibitory effect on α-amylase and α-glucosidase.