Objective To describe the prevalence of dental caries of children under 7 years old and its secular trend,and to analyze the relationship between dental caries and physical growth. Methods Subjects were from the national survey on physical growth and development of children under 7 years old in nine cities in 2015 (NSPGDC),whose primary teeth had been erupted.Dental caries and growth measurements were obtained in the field.The independent t-test was used to compare the difference of physical growth between children with and without dental caries.Moreover,the data of dental caries in NSPGDC in 1985 and 1995 were used to analyze its secular trend. Results 1) The prevalence of dental caries increased with chronological age,which was from 0.2% at 6~12 months group to 0.9% at 1 year group,to 45.7% at 6~7 years old group.2) The prevalence of dental caries in suburban children was higher than that in urban children and it was also higher in children from northern and southern region than that in central region.3) The differences of weight,length and body mass index between two groups with or without dental caries were not statistically significant for children under 3 years old (P>0.05),while,the three indicators in children aged 3~7 years old were lower in children with dental caries.4) From 1985 to 2015,the prevalence of dental caries became lower.Taking the 6~7 years old group in urban areas as an example,it was 68.1% in 1985 and 43.2% in 2015. Conclusions The prevalence of dental caries become higher and higher with chronological age and there is urban-suburban and regional difference.The relationship between dental caries and physical growth are more significant in children over 3 years old.And the prevalence of clental carries in nine cities is in decline.