Objective: To investigate the prevalence of deciduous dental caries in children aged 3 to 5 in Congjiang County, Guizhou Province, and to provide information support for oral health care for local government. Methods: According to the requirements of the Fourth National Epidemiological Survey of Oral Health, 1614 children aged 3 to 5 in Congjiang County were selected to calculate the prevalence, the mean dmft (decayed-missing-filled tooth) and the filled rate of the primary teeth. Statistical analysis was performed using SPSS 21.0 software. Results: The prevalence of dental caries in deciduous teeth, the mean dmft value and the filled rate were 94.18%, 8.34, 0.68% independently. There were significant differences in the prevalence of dental caries, the mean dmft and the filling rate between male and female and among different age groups. Conclusion: The children aged 3 to 5 in Congjiang County had a high prevalence of dental caries in primary teeth. Children aged 3 to 5 are the focus of early caries prevention for us. There is an urgent need for improvement about oral hygiene and oral health behavior for local residents.