Objective: To understand the awareness of sexual knowledge among primary and secondary school students, as well as their attitudes towards school sex education and to provide a reference for school-based sex education. Methods: A total of 5 531 primary and secondary school students were selected from Beijing, Chongqing, Heilongjiang (Harbin and Jiamusi) and Hubei (Wuhan and Xiaogan) by stratified cluster sampling and were investigated with self-reported questionnaire. Results: Sex-related knowledge scored 62.33±19.35, with a pass rate of 61.9%, and the excellent rate 17.5%. Sexual knowledge of junior high school students scored 64.30±19.07, with the pass rate of 64.7%, and the excellent rate 22.0%. A large proportion of primary students reported unaware of pubertal growth and HIV/AIDS-related knowledge, and a large proportion of junior high students unaware of reproductive physiology. Multivariate Logistic regression analysis showed region, grade, gender, and suburban areas were related to the level of sexual knowledge(P<0.05). More than 76.0% primary students and 85.9% middle school students agreed on the importance of school sexuality education. 59.7% of primary school students and 73.3% of junior high school students hoped to include school sexuality education in compulsory education courses; 59.8% of primary school students and 68.3% of junior high school students felt that school sexuality education should be equipped with specialized teachers. Conclusion Chinese primary and secondary school students are lack of sexual knowledge. As students have strong wills to get more information on sexual knowledge, schools should provide them with more comprehensive and effective sex education through appropriate courses and activities.