Objective To study the current situation of chronic diseases among island residents who have drunken desalinated water for a long time， and to reveal the relationship between drinking desalinated water and water from other sources and the prevalence of chronic diseases among the population.

Methods According to the different drinking water sources of island residents， the research subjects were divided into seawater desalination group （residents of Gouqi Township， Shengsi County）， mixed water source group （residents of Shengshan Town， Shengsi County） and freshwater group （residents of Huanglong Township， Shengsi County）. Through the chronic disease network report and resident health file system， the current situation of chronic diseases in different water groups was investigated and analyzed.

Results There were significant differences in the prevalence of malignant tumor among drinking water sources （χ²=23.867， P<0.001）， with the prevalence of mixed water group >desalination group >fresh water group. There were significant differences in the prevalence of coronary heart disease （χ²=194.883， P<0.001）， with the prevalence of mixed water group >desalination group >fresh water group. There were significant differences in the prevalence of stroke （χ²=35.637， P<0.001）， with the prevalence of fresh water group > mixed water group > desalination group. There was no significant difference in the prevalence of diabetes mellitus （χ²=2.808， P=0.246）， but there was significant difference in the age of onset of diabetes mellitus （χ²=7.368， P=0.001）， and significant difference in the prevalence of diabetes mellitus in the age group ≥55 （χ²=17.144， P<0.001）， and the onset age and prevalence were all in the order of fresh water group > desalination group > mixed water source group. There was no significant difference in the prevalence of hypertension （χ²=3.962， P=0.138）， but there was significant difference in the prevalence of hypertension in the age group ≥55 （χ²=20.734， P<0.001）， with the prevalence of fresh water group > desalination group > mixed water source group.

Conclusion Long-term consumption of desalinated water by residents is correlated with malignant tumors， coronary heart disease and stroke， and has no correlation with diabetes and hypertension.