Abstract: Gastric ulcer was duplicated in 40 Wistar rats by injection of 20% acetic acid under their gastric mucosae. Ten rats, stomaches were opened for observation every week after the injection. The results showed that the duplicated gastric ulcers were very typical and the incidence was as high as 100% within two weeks. The renovation of the ulcers was very fast during the 3 rd week, and by the end of the 3 rd week 4 cases of ulcer can be seen in 10 rats. At thw 4 th week there was only 1 case of ulcer in 10 rats, and the gastric mucosae were renovated markedly. The renovating course is similar to that of human gastr ulcers.