Abstract: Objective To understand the prevalence of dental caries in primary and secondary school students in Ganzhou district of Zhangye, Gansu province, and provide evidence for the effctive prevention of dental caries. Methods A total of 1200 students were selected through stratified cluster random sampling from two primary schools and two secondary schools. Dentists examed their teeth according to the third national oral health epidemiologic survey protoccl. Results The deciduous teeth caries rate was 50.75%, the filling rate of caries was 7.61% and the average caries number was 1.87. The permanent teeth caries rate was 16.08%, the filling rate of caries was 20.03% and the average caries number was 0.53. The differences in deciduous/permanent teeth caries rate and filling rate of caries between urban area and rural area were statisitcal significant. The deciduous teeth caries rate was negatively correlated with age, but the permanent teeth caries rate was positively correlated with age. Conclusion The prevalence of dental caries in the students was high. It is necessary to strengthen the health education about dental health in children and the cooperation between disease control sector and schools to prevent dental caries in students.