Objective: To investigate the prevalence of primary tooth caries among preschool children in Macau in 2025 and the associated factors, so as to provide a theoretical basis for formulating targeted oral health intervention strategies for children. Methods: From January to May 2025, a stratified random cluster sampling method was adopted to select two kindergartens from each of Macao s three regions (Northern Region, Central Region, and Southern and Outlying Islands Region), enrolling a total of 884 preschool children for dental health examinations and questionnaire surveys. Intergroup comparisons were performed by using the Chi-square test and t-test, and multivariable Logistic regression was applied to analyze the factors associated with primary tooth caries among preschool children. Results: Among the preschool children, the prevalence of primary tooth caries was 40.7%, the filling rate was 7.4%, the missing rate was 2.0%, and the mean dmft index was (1.77±3.14). Multivariable Logistic regression analysis revealed that being 3 years old ( OR =0.48), being 4 years old ( OR =0.63)，being an only child ( OR =0.61), having a weekend screen time of 30 to <60 min ( OR =0.61) or <30 min ( OR =0.56), maintaining a regular toothbrushing habit ( OR = 0.59 ), parental perception of the child being caries free ( OR =0.60), father having a postgraduate degree ( OR =0.56), and mother having a bachelor s ( OR =0.57) or postgraduate degree ( OR =0.66) were associated with lower risks of primary tooth caries among preschool children(all P <0.05). Conversely, having breakfast 3 to <6 days/week ( OR =1.48) or <3 days/week ( OR =2.80), weekly intake of high sugar foods/beverages ≥ 5 times ( OR =1.90), 3 to <5 times ( OR =1.86), or 1 to <3 times ( OR =1.67), having a oral examination in the past year ( OR =1.86), and parental awareness of the child having caries ( OR =1.35) were associated with higher risks of primary tooth caries among preschool children (all P <0.05). Conclusions The prevalence of primary tooth caries among preschool children in Macau is relatively high.Therefore, targeted intervention measures should be implemented to reduce the incidence of primary tooth caries in preschool children.