Objective To evaluate the effectiveness of prevention of dental caries in preschool children by family-based oral health management. Methods A total of 144 families with 3 years old children in Huangpu District were randomly divided equally into intervention group and control group.The intervention period was 2 years.Semi-annual oral health guidance was given to families in the intervention group(including oral examination, children′s deciduous teeth coating with fluoride, dental caries filling, oral health lectures for families, distribution of family oral health brochures, etc.)Families in the control group received annual oral examination.After the intervention, the parents completed their child′s oral health questionnaire. Results In the 2-year oral monitoring period, the incidence of dental caries in the intervention group and the control group was 9.72% and 22.22%, respectively within one year, and the difference between the two groups was statistically significant(χ²=4.19, P < 0.05).The incidence of dental caries was 12.50% and 36.11% within two years, and the difference between the two groups was also statistically significant(χ²=10.91, P < 0.01).Result of the questionnaire survey showed that children in the intervention group had better eating and oral health habits than the control group, and the differences between the two groups were statistically significant(P < 0.05). Conclusion Regular and professional family oral health management can effectively reduce the incidence of dental caries and improve the oral health in preschool children.