Subject:to study effects of fluorine and iodine in drinking water on children's intelligence development and its interaction, and the relation between children's intelligence development and the environmental and education factors. Methods: Randomly selected 8 ～ 14year old children in the endemic area and control areas as the investigate subjects,and inspected the prevalence of fluorosis and strums,IQ levels were also measured. Results:in endemic areas,if fluorine and iodine concentration were both high in drinking water,the diseases prevalence was higher,and it was higher than the areas of only fluorine or iodine concentration was high. The average IQ level was not significant lower. There was not significant difference between the areas where only flurine concentration was high and the fluorine and iodine were both high (P＞0.05) ;IQ level was significantly related with lower concentration ofiodine in drinking water ( P ＜ 0.01 ) ;and there were interaction between fluorine and iodine to IQ ( P ＜ 0.01). the children living in high fluorine areas, the IQ level were significantly related with their parents education level ( P ＜0.01). conclusion: it is a hazardous factor to health if fluorine and iodine levels are both higher in drinking water, and there were interaction effect between fluorine and iodine,the effect of fluorine to health was less than iodine;education and environmental factors can affected the development of intelligence.