Abstract: 　Objective To understand the difference of Demodex prevalence among medical students living and studying together with different classes, sexes and nationalities. \ Methods\ Demodex folliculorum and Demodex brevis were detected by using cellophane tape on the nasolabial grooves. \ Results\ The overall prevalence was 51.5% in 2 248 medical students. Prevalence in different classes and sexes was: freshman 42.6%, sophomore 49.6% and third year students 66.8%; 55.7% in males and 48.7% in females. Prevalence in students with different nationalities was: Mongolian 49.8%, Han 52.8% and other minorities 64.3%. \ Conclusion\ The Demodex prevalence in students of senior classes was higher than those from junior ones (P<0.01), higher in males than in females (P<0.01). Prevalence in Han students was slightly higher than in Mongolian with no statistical difference.

Key words: human Demodex, prevalence, student