Gastric ulcer or gastritis is a benign disease in the digestive system which is caused by a small ulcer in the inner lining and gastric mucosa. Among gastric ulcer characteristics is the deep ulcer that passes through the gastric mucosa. Almost all benign gastric ulcers are located in the anthrome (the lower stomach area). One of the methods to treat gastric ulcer is the use of medicinal herbs. Among effective medicinal herbs in treating gastric ulcer is Nigella sativa. The most important application of Nigella sativa is in inflammation reduction and wound healing acceleration. Substances such as linoleic oil, thymoquinone and antioxidants are obtained from nigella sativa. The rats were fed using a standard laboratory diet. Prior to surgery, the rats were deprived of food for 48 hours, and no water was given to them two hours before surgery. Gastric ulcer was generated by injecting acetic acid to stomach lining where there were no vessels. The oil at different doses was given to rats through gavage tube one day after gastric ulcer was generated. The rats were killed on days 4, 7, 10, and 14, and their stomachs were removed and the ulcer dimensions were calculated in terms of m2. Moreover, after cutting and providing lam, in order to conduct histological studies, samples were stained using hematoxylin and eosin and were examined by microscope. The obtained results showed that the percentage of wound healing in Nigella sativa at three doses (50, 100, 200 mg/kg) on days 4, 7, 10, and 14 had a significant increase in comparison to sham-operated and control groups (P<5%). Due to the presence of compounds such as terpenes, flavonoids, vitamins A, B, and C, and the anti-inflammatory and antioxidant properties in Nigella sativa, it facilitates the gastric ulcer healing, protects stomach tissue, and reduces gastric inflammation and ulcer, and has a greater restorative effect on gastric ulcer caused by acetic acid.