In this work, crude polysaccharide extracts were extracted from pumpkin (Cucurbita moschata) fruit by hot water. After removal of proteins and purification, polysaccharides of pumpkin fruit (PP1-1) were subjected to structural identification. Gas chromatography analysis indicated that PP1-1 comprised of galactose (86.4%), and glucose (13.6%). The molecular weight of PP1-1 was measured to be 0.87 × 104 Da by gel permeation chromatography. The inhibitory kinetic evaluation showed that it was non-competitive inhibition of PP1-1 on the α-glucosidase-catalysed hydrolysis of PNPG. The Michaelis–Menten constant (Km) was 0.106 m, and the inhibitory constants (Ki), 0.435 mg.