Objective To compare the caries status of preschool children's deciduous teeth in a district of Shanghai in different periods,and to provide scientific basis for optimizing the prevention and control strategies of children's caries.Methods The oral health monitoring cohort of 3-year-old children was established in 6 kindergartens in a certain district of Shanghai from 2020 to 2022,and compared with the cohort in 2005.Results A total of 412 preschool children were examined in this survey,and the cumulative incidence from 2020 to 2022 was 28.67%.The caries prevalence rate,DMFT index and CSI index of children in the cohort in 2020 were lower than those in the cohort in 2005,and the difference was statistically significant(P<0.05).Although the dental caries filling ratio of children in different cohorts has increased with age,it is still at a low level.Conclusion The preventive measures of dental caries among preschool children in Shanghai have achieved some results,and the caries rate has decreased.However,the situation of prevention and control is still grim,and the filling rate of dental caries is still at a low level.More effective measures are needed to improve the caries situation of preschool children.