Abstract: Objective To study the changing and its interaction of determining serum gastrin levels and Helicobacter pylori test during chronic atrophic gastritis into gastric cancer. Methods RIA and ¹³C-urea breath test(¹³C-UBT) determined the Gs levels and Hp infection rate in 63 rate cases(first visit) patients,48 cases(after one year return visit) patients, 35 cases(after three year return visit) patients and 30 cases(after five years return visit) patients with CAG 90 cases patients with gastric cancer(and different position) and 61 cases normal controls. They all were done study compared. Results Serum Gs levels in 63 cases(first visit) patients, 48 cases(after one year return visit) patients, 35 cases(after three year return visit) patients and 30 cases(after five years return visit) patient with CAG were significantly higher(t=4.716, 5.218,5.624, 6,179, 6,572, all P<0.01) than 61 cases normal controls, but Hp infection rate were 65,1%, 70,8%,82.9%, 86.7% and 88.8%. There was no distinct difference between serum Gs in patients with sinuses ventriculi cancer and normal controls(t=1.560, P>0.05). Serum Gs levels in 90 cases with gastric cancer(and different position) was significantly higher(t=4.221, P<0.05; t=4.436, P<0.01) than 61 cases normal controls and the highest serum Gs level was found in cancer of cardia and fundus. And Hp infection rate was 88.8%. Conclusion The early diagnosis on gastric cancer was very important by determining serum Gs and Hp infection rate.