Objective To observe the effect of fresh yam extract on the ulcer index, mucosal morphological structure, expression of serum superoxide dismutase ( SOD) and glutathione peroxidase ( GSH-Px ), malondialdehyde (MDA), and nitric oxide (NO) in mice with gastric ulcers and explore the mechanism of its prevention and treatment of gastric ulcers. Methods We randomly divided 100 mice into blank control, model, teprenone, and high and low dose fresh yam extract groups. Normal saline was administered to blank control and model groups, and experimental drugs were administered to the other three groups for 45 days. Then, the gastric ulcer model was established by one intragastric administration of anti-inflammatory pain (2. 5 mg / mL) in the groups except the blank control group. All mice were sacrificed after 7 h. The activities of SOD and GSH-Px, and NO and MDA in serum were detected by blood sampling. The ulcer index was measured, and the ulcer inhibition rate was calculated. Pathological sections of gastric tissue were prepared from the whole stomach and stained with HE, and morphological changes of the mucosal tissue were observed. Results Compared with the model group, high dose, low dose, and teprenone groups had reduced gastric ulcers caused by indolence pain, and inflammatory cell infiltration and destruction of the glands in gastric tissue were less. In the high dose group, MDA and NO were decreased in serum, and expression of SOD and GSH-Px was increased (all P<0. 05). Conclusions Fresh yam extract prevents acute gastric ulcers and protects the gastric mucosa, and its mechanism may be related to reducing the serum contents of MDA and NO, and increasing the expression of SOD and GSH-Px for anti-oxidative stress effects.