The epidemic tendency of dental caries of school students over the past 15 years in China was analyzed in order to provide bases for prevention of dental caries. Data sets of boys and girls at the age of 7, 9, 12 years (deciduous caries) and 7, 9, 12, 14, 17 years (permanent caries) were collected from the series of Chinese National Surveillance on Students' Constitution and Health (CNSSCH) between 1991 to 2005, a survey that covers 30 provinces of and autonomous regions of China, with Tibet Autonomous Region and Taiwan Province excluded owing to unavailability of related data. According to their socioeconomic status, three urban regions and three rural regions (province capital must be included) were selected in each province, where its socioeconomic status and sports exercise can represent the general level of the locality. All subjects were Han students. Prevalence of deciduous and permanent caries was measured. In 2005, the prevalence of deciduous caries at 7, 9, 12 years was 52.87%, 52.04% and 9.80% in urban boys, 59.37%, 58.68% and 12.18% in rural boys, and that of permanent caries in boys at 7, 9, 12, 14, and 17 years was 2.35%, 5.63%, 13.94%, 19.05% and 21.29% in urban boys, 3.42%, 7.26%, 13.35%, 16.16%, 18.55% in rural boys, while in girls at the same age groups, the prevalence of deciduous caries was 53.53%, 49.48%, 7.92% in urban girls, 59.95%, 56.13%, 8.85% in rural girls; the prevalence of permanent caries was 3.61%, 8.99%, 19.32%, 24.75%, 28.62% in urban girls, and 3.47%, 10.65%, 17.66%, 22.52%, 24.27% in rural girls. The epidemic manifested a gradient distribution in age groups, which was closely related to region of the study population. A dramatic decreasing trend was witnessed among all sex-age subgroups in the rural groups between 1990 and 2005, and such a trend was stronger in deciduous caries than in permanent caries, however, this kind of decreasing trend was not steady, because there was bounce during some year. Although the morbidity of dental caries in China is lower than the standard set by the World Health Organization, and the prevalence of dental caries decreased from 1991 to 2005, the prospect of epidemic dental caries in China is in no way optimistic. The total population with dental caries is still very large and the prevalence decreased unstably. Therefore, financial support on school oral health care should be increased, and a national school oral health service network should be set up.