A hospital-based cross-sectional study in SIGES project was conducted during 2016.5-2017.5 in West China Hospital. It was aimed to observe the prevalence of atrophic gastritis (AG) in southwest China, and assess the diagnostic strength of serum gastrin-17 (G-17) in predicting AG in Chinese population. Asymptomatic healthy controls from health checkup , cancer-free patients with unspecific upper gastrointestinal symptoms, and histologically proven gastric cancer patients were eligible, if serum pepsinogen-I (PG-I), PG-II, and G-17 were detected. AG status was classified by the accredited cutoffs of PG-I (<70 ug/L) and PG-I/II ratio (<3). Totally, healthy controls (n = 9,425), symptomatic patients (n = 671) and gastric cancer patients (n = 305) were simultaneously observed, in which the prevalence of AG in southwest China were estimated as 15.9/1,000, 28.3/1,000, and 55.7/1,000 persons, respectively. The age-specific prevalence of AG in healthy controls showed a significantly uphill trend (p for trend <0.001). Higher level of serum G-17 was significantly associated with increased risk of AG in healthy population (15-30 pmol/L, aOR = 20.67, 95% CI 9.17-46.55; >30 pmol/L, aOR = 314.41, 95% CI 166.10-595.12). Throughout the progression of stomach diseases, the diagnostic strength of serum G-17 for AG showed a downhill trend across more advanced situations. In despite of that, serum G-17 displayed a good performance in predicting AG in the entire cross-sectional population (AUC = 0.92, 95% CI 0.89-0.94; SEN = 85.5%; SPE = 93.2%; LR+ = 12.55; LR− = 0.11). Population in southwest China had intermediate prevalence of AG, while the prevalence was increased over age or disease progression. High level of serum G-17 might be a reliable non-invasive measurement to predict AG in southwest Chinese population. Atrophic gastritis is a well-established precursor of intestinal-type gastric cancer. The population prevalence of atrophic gastritis generally ranged from 2.1% to 8.2% 1. The presence of atrophic gastritis was associated with the increased risk of gastric cancer during longitudinal observation in both the western and eastern populations 2-4. Therefore, the China Consensus on Early Gastric Cancer Screening, Endoscopic Diagnosis and Treatment (2014) recommended to define patients with atrophic gastritis as a kind of high-risk candidates for gastric cancer screening 5. The European Helicobacter Study Group agreed on the statement "Serologic screening is suitable for clinical use in countries with a relatively low incidence of gastric cancer, because it enables endoscopic follow-up of caseswith an abnormal serologic profile suggesting atrophic gastritis" 6. However, nationwide massive screening programs for gastric cancer were established only in Japan and Korea, but not in China and other nations yet 7,8. Regarding the great health burden from gastric cancer in China 9,10 , particularly the relatively low proportion of early gastric cancer 7,11 , it would be necessary to investigate the relevant screening strategy covering pr...