Present study was designed to find the physicochemical and functional properties of fermented yam (Dioscorea) solution by Streptococcus thermophilus and protective effect on stomach lesions. The solutions of raw and extracted yam used were 2, 4, and 6%, and they were fermented by S. thermophilus for 32 h. The fermented extracted yam showed a lower value of viscosity than the raw and maintained this throughout the fermentation. The yam (Dioscorea opposita Thunb.) raw powder in the functional components showed higher allantoin content compared with the extracted powder. In the animal study, the gastric lesions were apparently reduced compared with those in the control rats when 200 mg of powder/kg BW was injected. Based on these data, the present study indicated that the raw yam powder fermented by S. thermophilus showed a protective effect on gastric lesions in rats, therefore, it could be supplemented to functional food.