The Department of Epidemiology currently has 7 staff members (2 senior researchers, 1 associate senior researcher, 2 intermediate researchers, and 2 junior researchers) and over 10 graduate students. It has successively undertaken national key science and technology projects from the "6th Five-Year Plan" to the "11th Five-Year Plan," the National "973" and "863" Programs, the Ministry of Science and Technology's Key R&D Program and International Cooperation Projects, the National Overseas High-Level Talent Program Fund, the National Natural Science Foundation of China's International (Regional) Cooperation Fund and General Projects, as well as collaborative projects with the U.S. National Cancer Institute (NCI) and the Technical University of Munich, Germany. The department has published over 250 papers, including in internationally renowned journals such as *Lancet*, *BMJ*, *Nature Medicine*, *Gastroenterology*, *Gut*, *JNCI*, *Cancer Research*, *Endoscopy*, *JAMA Netw Open*, and *EBioMedicine*. It has received 2 National Science and Technology Progress Awards and 15 awards from the Chinese Medical Association, the Ministry of Education, and the Beijing Municipal Science and Technology Progress Awards. The department has long been engaged in cancer epidemiology research. Since 1983, in collaboration with the U.S. NCI, it has conducted a series of studies on the etiology, pathogenesis, and prevention of gastric cancer in Linqu County, Shandong Province—a high-risk area with unique research value. These studies have clarified the epidemiological characteristics of gastric cancer in China and identified risk and protective factors. Through large-sample and prospective studies, it has further confirmed that gastric carcinogenesis is a multi-stage process influenced by multiple factors. Additionally, randomized controlled intervention trials targeting gastric cancer etiology—including *Helicobacter pylori* eradication, nutrient and allicin supplementation, and COX-2 inhibitor administration—have been conducted. After 22.3 years of follow-up, it was confirmed that *H. pylori* eradication effectively reduces gastric cancer incidence and mortality. This series of findings has become a key basis for the WHO-IARC's "Strategy for Gastric Cancer Prevention through *H. pylori* Eradication," making a significant "Chinese contribution" to gastric cancer prevention. Building on this, in collaboration with the International Digestive Cancer Alliance (IDCA) and the Technical University of Munich, the department conducted the world's largest intervention study on *H. pylori* eradication for gastric cancer prevention in a community population of 180,000. After 11.8 years of follow-up, the successful eradication group showed a 19% reduction in gastric cancer incidence, with reductions of 35% and 43% in incidence and mortality, respectively, among individuals aged 25–45. Published in *Nature Medicine*, this study garnered international attention, with *Science* providing in-depth coverage as a NEWS feature and *Nature Reviews Cancer* highlighting it as a Research Highlight. It was also named one of the "Top Ten Clinical Research Achievements in the Chinese Gastrointestinal Field" for 2023–2024. Furthermore, leveraging the high-risk gastric cancer area, the department has implemented gastric cancer screening and early diagnosis and treatment programs, scientifically evaluating screening effectiveness and strategies. Using biospecimens from long-term cohort follow-ups, multi-omics technologies have been employed to identify biomarkers closely associated with gastric cancer and precancerous lesion progression, providing a basis for early warning and screening in high-risk populations. These findings have laid a crucial foundation for understanding the natural history of gastric cancer, the evolution of precancerous lesions, and the development of prevention strategies. The research has been widely reported by mainstream domestic and international media, including the *New England Journal of Medicine*, China Central Television (CCTV), and *China Youth Daily*. The department places great emphasis on graduate education, actively fulfilling the fundamental task of fostering virtue through education. Over the years, it has trained nearly 70 doctoral and master's students. Through extensive academic exchanges, it fosters a scholarly atmosphere and creates learning opportunities for graduate students and young researchers. In terms of international collaboration, the department has established a long-term partnership with the Technical University of Munich, Germany. In 2017, it successfully applied for the German Federal Ministry of Education and Research (BMBF) "Forschungspräsenzen" program, jointly establishing the "Upper Gastrointestinal Cancer" Joint Key Laboratory—the only biomedical key laboratory among the eight Sino-German joint projects approved by BMBF. Based on this BMBF project, in collaboration with Peking University Health Science Center, it applied for and was approved as a National International Cooperation Base by the Ministry of Science and Technology. In 2025, it was designated as a Beijing International Science and Technology Cooperation Base. **Main Research Directions:** The primary research directions of the Department of Epidemiology focus on the etiology, pathogenesis, early diagnosis, and prevention of gastric cancer. Aiming to address practical issues in gastric cancer prevention and treatment, the department combines field studies in high-risk areas with laboratory research. Through large-scale population studies, it elucidates the mechanisms and preventive pathways of gastric cancer and precancerous lesion development at the high-risk population, individual, and molecular levels. Key research areas include: 1. Establishing a high-risk gastric cancer field site in Linqu County, Shandong Province, to conduct descriptive, analytical, prospective, early diagnostic, interventional, and molecular epidemiological studies. These investigations explore the risk factors, pathogenesis, and prevention of gastric cancer. Prospective studies have examined the progression of precancerous lesions and their relationship with gastric cancer, further identifying environmental and host risk factors. Multiple intervention studies, including *H. pylori* eradication, have been conducted in high-risk populations. 2. Establishing a large-scale long-term follow-up and intervention cohort in the high-risk gastric cancer area. Through over 20 years of dynamic follow-up, a substantial collection of biospecimens has been obtained, providing a critical foundation for molecular epidemiological research. Utilizing these long-term preserved biospecimens, big data and multi-omics technologies are employed to screen for gastric cancer-related molecular biomarkers. Combined with intervention studies, the effects of chemopreventive interventions are objectively evaluated at the molecular level. 3. Conducting early diagnostic screening studies for gastric cancer in high-risk areas to identify molecular biomarkers for early warning and diagnosis in high-risk populations. These studies also explore screening and early diagnosis and treatment strategies tailored to China's national conditions.