Objective To evaluate the prevalence of dental caries and oral health behavior among preschool children in Zhangjiagang,and to provide evidence for prevention of dental caries. Methods A total of 1 405 preschool children from 16 preschools in Zhangjiagang were selected by the means of random,stratified and cluster sampling.Dental caries was diagnosed by oral examination and questionnaire survey was conducted among their parents.The results were analyzed by Logistic regression analysis. Results The prevalence rate of caries was 61.99%,the mean number of decayed,missed and filled teeth (dmft) was 2.81,the filled rate was 3.54%.The caries prevalence rate of boys and girls were 63.21% and 60.63% respectively,and the difference was not statistically significant (P>0.05).The rate of urban and rural was 60.86% and 63.36% respectively,the difference was also not statistically significant (P>0.05).As the growth of the age,the rate also increased,there was statistically significant difference between different age groups (χ²=39.470,P<0.05).The ratio of children who began to brush their teeth before 3 years old was 30.25%,but only 1.00% started brushing when they were 6 months,While 18.78% brushed occasionally or even never brushed.The ratio of children who never ate sweet food before sleeping was only 23.42%.High frequency of eating sweet food before bedtime and began to brush teeth later were important risk factors for dental caries,the differences were both statistically significant(χ²=9.740,14.913,P<0.05). Conclusion The prevalence rate of caries among preschool children in Zhangjiagang is high,and their oral health behavior is poor,so it is necessary to strengthen oral health education for both children and parents.