Abstract: Objective　The study was conducted to investigate the AIDS related knowledge among middle school students and to provide evidence for the development of effective health education on AIDS and sexual activity. Methods　An anonymous questionnaire based survey was performed in a cluster randomized sample of students from four grades of eight secondary schools in Lucheng District in April, 2007. Results　A total of 465 middle school students were surveyed, the overall awareness rate of AIDS being 74.93%. The rate in men (71.61%) was lower than that in women (78.32%, P0.01). The correctness rate was higher among senior students than junior ones (P0.01). Students of higher grades showed higher awareness rates of HIV/AIDS transmission route, which were significantly higher than those of non transmission routes (P0.01). 1.72% of the students had sexual activities, and 6.25% of them had one partner while 12.50% of them had two. 12.50% of them did not use condoms in the last sexual intercourse; 12.50% of them had made or got pregnant. Conclusion　The awareness of AIDS among middle school students suggests insufficient knowledge of AIDS, in particular, misunderstanding in sexual knowledge, in this group. Therefore, further health education on the prevention and control of AIDS, especially the non transmission routes of AIDS and sexual behaviors, should be strengthened.