Abstract: Objective To investigation the deciduous crossbite in Changning districe of Shanghai，thus to provide theoretical basis for prevention and treatment of malocclusion. Methods Randomly select one street in the east, middle and west of Changning District. 2 kindergartens were randomly selected from each street. Based on individual normal defects. Investigation of deciduous teeth in 830 children aged 4-6 years in 6 kindergartens. Statistical analysis of data using spss19.0. Results Prevalence of deciduous crossbite was 12.41%. There is no significant difference between male and female children aged 4 and 5 years old. The deciduous rate of 6-year-old girls is significantly higher than that of boys. The main manifestation of deciduous crossbite is that individual anterior crossbite. accounts for 44.66%. The treatment rate of deciduous crossbite only 1.94%. Conclusion Deciduous crossbite is common oral diseases in preschool children. The rate of 6-year-old children is significantly higher than that of 4 and 5 years old. Early treatment is recommended for 3-4 years old.

Key words: deciduous crossbite, prevalence, early treatment