To explore the relationship between high altitude polycythemia (HAPC) and peptic ulcer bleeding, in order to provide the evidence for the clinical diagnosis and treatment of peptic ulcer disease in Tibet of China. A retrospective case-control study was conducted. Patients who hospitalized in the Department of Gastroenterology with the diagnosis of peptic ulcer bleeding from January 1, 2015 to April 30, 2021 in Tibet Autonomous Region People's Hospital were enrolled in the case group, and patients who hospitalized in the Department of Urology without tumor and without the history of peptic ulcer and gastrointestinal bleeding during the same period were selected as the control group. In the study, 1 ∶ 1 case matching was conducted between the two groups according to the gender, age (±2 years), ethnic group (Tibetan, Han), and the residence altitude level (grouped by < 4 000 m or ≥4 000 m), and 393 cases were included in the case group and the control group respectively. All the patients had lived in Tibet with