AIM:To investigate the relationship between different sources of drinking water supply, water quality improvement and gastric cancer mortality rate in a high risk area.METHODS: A retrospective-cohort survey was carried out in all towns of this county to study the effect of different sources of drinking water supply and water quality improvement on gastric cancer mortality rate.RESULTS: The gastric cancer mortality rate among the population 124.05/10(5) drinking river water was obviously higher than that of drinking shallow well water (74.85/10(5)) (P < 0.01) according to the Zhanggang Town 16 years accumulated data. The same pattern was presented in 7 towns after balancing the confounders. The gastric cancer mortality rate of population drinking river water was 86.03/10(5), which was higher than those drinking shallow well water (62.03/10(5)) and tap water (29.78/10(5))(P < 0.01). When the drinking water switched from river and well water to tap water, the gastric cancer incidence decreased to 30.33/10(5) and 26.10/10(5), and the gastric cancer mortality decreased by 59% and 57% respectively.CONCLUSION: The quality of drinking water is one of the important factors of increased incidence of gastric cancer in Changle County, and water quality improvement has a beneficial effect, but the cause of high gastric cancer incidence may be multi-factorial in this area.