Abstract: Objective To understand the prevalence of caries in 351 children aged 5 years in Haidian district of Beijing and provide evidence for the children oral health care. Methods A total of 351 children aged 5 years, including 174 boys and 177 girls, were selected through multistage stratified cluster random sampling in Haidian. The caries on the crowns of deciduous teeth were assessed according to the Guideline for the 3rd National Oral Health Survey. Results The prevalence of caries was 64.10%. There was no significant difference in caries rate between boys and girls (P0.05). Only 31.54% of the cavities were filled, this rate was significantly higher in girls than that in boys (P0.05). Conclusion The prevalence of caries was high in children aged 5 years. Attention should be pay to oral health of preschool aged children. Parents should help their children in improving oral health awareness and developing good oral health habit. And it is necessary to conduct regular oral health examination in preschool aged children for the early detection and treatment of caries.