Gastric ulcers are generally small, more than half of patients have gastric ulcers <2cm in diameter, and those >2.5cm in diameter are giant ulcers, which do not heal easily over time and have a certain tendency to become malignant. Giant ulcers require biopsy, and biopsies taken at the edge of the ulcer, where the tissue is hyperplastic, are easy to get the lesion tissue and have a higher positive rate. Under endoscopy, for ulcers with uneven bottom, necrotic tissue, bleeding, surface covered with filthy moss, nodule-like elevation around the periphery, stiff and irregular periphery, jagged and volcanic dike like ulcers should be highly suspected of malignancy and biopsy must be taken to exclude malignant ulcers.