Response surface methodology was used to optimize extraction parameters for Morchella esculenta SO-01 exopolysaccharide (EPS) produced during submerged culture. The optimum conditions for EPS extraction were predicted to be, concentration at 84.07 degrees C, precipitation for 22.19 h and pH 8.44, and EPS production was estimated at 5.45 g/L. The actual yield of EPS under these conditions was 5.32 g/L The antioxidant capacity of the EPS was measured in vivo after filling the stomach with different doses of EPS and results showed that the activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) of blood, spleen, liver, heart, and kidney were increased by 125%, 46.11%, 23.33%, 12.19%, 41.29%, and 63.24%, 63.12%, 166.54%, 98.01%, 57.68%, respectively, and that malonaldehyde (MDA) of blood, spleen, liver, heart, and kidney were decreased by 21.80%. 67.84%, 28.48%, 56.15%. 41.62%. The results provide a reference for large-scale extraction of EPS by M. esculenta SO-01 in industrial fermentation. (C) 2010 Elsevier Ltd. All rights reserved.