The etiology of gastric ulcer is multifactorial, and the main causative factors are Helicobacter pylori (HP), drugs, abnormal mucosal defense and repair, genetic susceptibility and some other factors. HP is an important causative factor for gastric ulcers. The HP positivity rate for gastric ulcers is 60% to 90%, and the prevalence of gastric ulcers is higher in people with high HP positivity rate. Eradication of HP not only helps the healing of gastric ulcer but also significantly reduces the recurrence of ulcer. Patients taking long-term NSAIDs, glucocorticoids, and lupigrel are prone to gastric ulcers. Among them, NSAIDs are the most commonly used drugs that cause gastric ulcers, including ibuprofen, indomethacin, and aspirin. The defense and repair function of the gastric mucosa is very important to maintain the integrity of the mucosa and promote ulcer healing. Reduced mucosal barrier defense is the main pathogenesis of gastric ulcers. Impaired defense function and decreased repair ability both have an impact on the occurrence and regression of ulcers. Some patients with gastric ulcers have a significant family history and a genetic susceptibility. Some other causes such as heavy alcohol consumption, chronic smoking, and stress are common triggers of gastric ulcers. Patients with gastric lithotripsy develop gastric ulcers due to chronic mechanical frictional irritation from gastric stones. It can also occur in combination with other diseases, such as gastrogastrinoma, Crohn’s disease, liver cirrhosis, chronic obstructive pulmonary disease, shock, systemic infection, acute myocardial infarction, stroke, etc. Therefore, there are many causes of gastric ulcers, and for patients with gastric ulcers, removing the causes is also an important measure in their treatment.