Pumpkin polysaccharides (PPe) have a variety of bioactive effects and our previous research showed the acid hydrolysate (PPe-S, a mixture) from PPe had an antioxidative capacity both in vitro and in viro. The aim of this study was to purify PPe-S and investigate the antioxidant stress effects of 2 purified components (PPe-S-1 and PPe-S-2) using Caenorhabditis elegans as model organism. The results showed that PPe-S-2 had a notable antioxidant effect, and could significantly enhance the activities of antioxidant enzymes including superoxide dismutase (SOD) (P < 0.01), catalase (CAT) (P < 0.01) and glutathione reductase (GR) (P < 0.05), and increase the level of glutathione (GSH) (P < 0.01), and decreased the content of malondialdehyde (MDA) (P < 0.05). PPe-S-2 could significantly extend the survival time of C. elegans (P < 0.01), which were stress-induced by hydrogen peroxide and methyl viologen. PPe-S-2 was a heteropolys accharide composed of glucose, arabinose, rhamnose and galactose with the molar ratio of 1.00:0.03:0.02:0.14. The molecular weight of PPe-S-2 was 0.73 kDa detected by high performance liquid chromatography. These studies demonstrated that PPe-S-2 obtained by the acid hydrolysis of PPe had a prominent protective effect to the damage induced by the intracellular free radical generating agents.