Abstract: Objective To assess the relationship between drinking water fluoride levels and dental fluorosis,dental caries in school children aged 8-12 in Xi'an,and to provide reference for effectively protecting and improving teenagers' oral hygiene.Methods Twenty villages were selected as the investigation subjects from rural area with different levels of water fluoride in the endemic fluorosis areas.A cross-sectional analytical study was conducted on school children aged 8-12 years,the dental fluorosis and dental caries in children were detected.Results The prevalence of dental fluorosis among the surveyed children was 22.71%,and prevalence and severity of dental fluorosis were significantly increased with increasing fluoride content in drinking water(x2 =171.37,P<0.01),the rate was over 30% in the two groups which the water fluoride content was under-standard(1.0~<1.5,≥1.5 mg/L),the highest prevalence rate was 50%.A total of 929 children were examined and the rate of dental caries was 28.20%,there were significant association between drinking water fluorine concentration and dental caries(x2 =36.24,P<0.01).The rates were 39.14%,26.22%,24.81%,24.41% and 15.17% in the five groups.Caries prevalence was significantly increased when the water fluoride lower than 0.2 mg/L.The gender of child had any influence on the prevalence of dental fluorosis (x2 =0.48,P>0.05),the prevalence rate of dental caries was higher that in girls(x2 =6.82,P<0.05).Conclusion The appropiiate water fluoride concentration should be 0.2-1.0 mg/L for dental fluorosis and dental caries prevention.Surveillance on the dental caries should be enhanced in the region which the water fluoride was lower than 0.2 mg/L.