The optimum enzyme-assisted extraction conditions of cup plant (Silphium perfoliatum L.) polysaccharides (CPP) were obtained by response surface methodology (RSM), and were found to be an enzymatic hydrolysis time of 66 min, a liquid-solid ratio of 22 mL/g, pH 5.1, and an enzyme-complex dosage of 1.59 %, allowing a CPP yield of 13.69 %. DEAE-52 cellulose and Sepharose CL-6B columns were used to purify the CPP. A purified polysaccharide component, CPP-1.2, was obtained and further analyzed for its characteristics, antioxidant properties, and hypoglycemic activity. The monosaccharide composition of CPP-1.2 was mannose, galacturonic acid, glucose, galactose, and arabinose with a molar percentage ratio of 2.24:16.34:44.17:24.28:12.97. The 1,1-Diphenyl-2-picrylhydrazyl (DPPH) and 2,2-Azino-bis-(3-ethyl-benzothiazoline-6-sulfonic acid) (ABTS) radical scavenging abilities of CPP-1.2 (1.0 mg/mL) reached 95.20 % and 93.69 % that of ascorbic acid (1.0 mg/mL), respectively. Moreover, CPP-1.2 presented significantly higher inhibitory properties on the activities of alpha-amylase and aglucosidase than acarbose at each concentration tested. These results suggest that CPP-1.2 possesses the potential to be used as an antioxidant and hypoglycemic agent.