Abstract: Objective To understand the situation of HIV prevention knowledge and sexual education among junior high school students in Lhasa City, and to provide basic data and information for the adolescent physiological health and sex education courses in Tibetan junior middle schools.Methods Cluster sampling was carried out and 809 students in 2 junior high schools in Chengguan district of Lhasa were selected randomly in December 2015, the students answered the questionnaire which named"A questionnaire on the situation of adolescent physical health and sexual health education among junior high school students".Results The junior high school students have a very low awareness of reproductive organs (< 50%) and HIV prevention knowledge; 63.3%, 51.3% and35% of the students thought that HIV can be transmitted through dining, handshaking and study together respectively; 69%, 35.5%and 74%% of the students were shy, fearful and confused about menstruation and nocturnal emission respectively; only 50.8% of the students thought it was dangerous to meet friends via Network. Students with Tibetan nationality had lower awareness rate and risk prevention consciousness than students with Han nationality (P < 0.05).Conclusion The level of adolescent physiological health knowledge and HIV prevention knowledge is low among junior high school students in Lhasa, it should be popularize the contents of adolescent physiological health and sexual education, risk prevention consciousness and drug prevention education for every student.