Extraction and antioxidant activity of polysaccharides from the Chinese watermelon was investigated. The polysaccharides were obtained by hot water extraction, ethanol precipitation, and deproteinization with HCl, respectively. The molecular weight was 3.02 × 104. It showed by high performance liquid chromatography (HPLC) and TLC that Chinese watermelon polysaccharides consisted of six monosaccharides, namely glucose, galactose, mannose, xylose, arabinose, and rhamnose. The polysaccharides contained the β-glycosidic bond. Moreover, it was proved that the polysaccharides had high scavenging ability to superoxide anions.