In the current study, the structural and antioxidant activities of polysaccharides were characterized from soybean sprouts grown in the presence or absence of light. The crude polysaccharides, PL (polysaccharides from light-grown sprouts) and PD (polysaccharides from dark-grown sprouts), were extracted by hot water method, and were further purified by chromatography of DEAE-52. Under scanning electron microscope, the smooth surface of PL was distinct from that of PD. Two purified fractions (PD and PD3), although both were mainly composed of arabinose, xylose, mannose, glucose and galactose, had different molecular weight, 126.61 vs. 111.94 kDa, respectively. In vitro, stronger 2,2-diphenyl-1-picryl-hydrazyl (DPPH) radical scavenging activity and ferric reducing activity power (FRAP) were observed in PI3 compared with PD3. These results indicate that light treatment can significantly enhance polysaccharides' antioxidant activity. This work also provides a scientific basis for the further exploitation of polysaccharides from soybean sprouts grown in the light. Light treatment may have a potential application in vegetable processing industry. (C) 2015 Elsevier Ltd. All rights reserved.