Abstract: Objective To investigate the characteristics of children with primary dental caries aged 3-5 years old and their oral hygiene behaviors at department of stomatology of Baojing County People's Hospital. Methods A total of 1 879 children aged 3-5 years old with primary dental caries at department of stomatology of Baojing County people's Hospital were recruited from 2013 to2020. The dental caries of the children were examined and related information was recorded. Their oral hygiene behaviors and factors related to primary dental caries of them were investigated. Results 6 445 dental caries in 1 879 children were bilateral symmetrical,at the same time,maxillary deciduous central incisor,bilateral maxillary and mandibular molar were prone to dental caries. Prevalence of caries in boys was higher than that in girls,while prevalence of caries among children in rural area was significantly higher than that among children in towns,and caries increased with age. 67. 32% of those children adhered to brush teeth from about 3-years old.81. 80% of them brushed teeth≤1 time per day. 58. 97% of them brushed teeth for less than 1 minute each time. Only 0. 64% of them brushed their teeth correctly. 89. 25% of the children used toothpaste,and among them only 0. 12% parents confirmed their kids to use fluoride toothpaste. 94. 84% of the children would not brush teeth after eating before sleeping. 34. 97% used to sleep with feeding bottle. Conclusion The severity of primary dental caries among children at the department of stomatology of Baojing County People's Hospital is significantly than that in developed areas. Oral health advocacy should be strengthened to help family develop good oral hygiene habits,and regular oral health examination should be conducted to effectively reduce the occurrence of primary dental caries.