Abstract: Objective To understand dental caries and oral health behavior among primary students in Macao.Methods Data from "Macao Citizen Constitution Monitoring Report" included 5 240 pupils (2 872 boys, 2 368 girls).According to the requirement of "2015 Macao Citizen Constitution Monitoring Guidebook", dental caries was inspected through mouth mirror and probe by clinical dentists.Oral health habit was self-reported.T test, Chi-square test and Logistic regression model was used to statistical analysis.Results Among the 6-12 years old pupils in Macao, 58.7% had dental caries.Children who did not brush their teeth every day had 1.28 higher risk of caries risk than those who brushed teeth every day.The probability of dental caries had 42.4%lower risk of dental caries among those who brushed teeth and flossing every day than those who brushed teeth without floss every day.Dental caries was found 42.5% higher among those who visited dentist clinics compared with those who did not visit dental clinics.The figure was 29.8% among those who already had dental caries before visiting dental clinic.About 34.2% of children had tooth decay in primary molars.Conclusion There are 58.7% Macao pupils aged 6 to 12 years old having tooth decay.Brushing and flossing everyday can help keep teeth clean and prevent decay tooth.The Macau primary students have not paid enough attention to oral health or regular dental examination, only after dental caries occurred.