The purpose of the present research was to compare the effects of four extraction methods on the extraction yields, physicochemical characteristics, and antioxidant activities of polysaccharides from the cup plant (Silphium perfoliatum L.) (CPPs). The extraction methods included the hot water extraction method (HEM), ultrasonic-assisted extraction method (UEM), enzyme-assisted extraction method (EEM), and the ultrasonic-enzyme-assisted extraction method (UEEM). Four corresponding CPP extracts, HEM-CPPs, UEM-CPPs, EEM-CPPs, and UEEM-CPPs, were obtained. The results indicated that there were notable differences between the extraction methods regarding the yield, average molecular weight, uronic acid content, monosaccharide proportions, and the antioxidant activities of the CPPs. HEM-CPPs were extracted with the lowest yield (6.44%). EEM-CPPs had the largest extraction yield (9.87%) and the most notable antioxidant abilities of ferric reducing power and free radical scavenging activity. According to correlation analysis, the higher antioxidant abilities of EEM-CPPs might be due to their smaller average molecular weight and a higher content of uronic acid than those of the other extracted CPPs. Therefore, EEM could serve as a promising technique for extracting CPPs.