Using cellophane adhesive-tape method, an investigation of demodicid infestation in 2160 students was carried out in Changsha of Huanan province, China. The results shows that the total infestation rate was 19.68%, that there was no significant difference in the demodicid infestation rate between male and female students, the infestation rate of university undergraduates was higher than that of high school students and that most of them were infested with Demodex follicuorum. The detection rate (51. 52%) for three-time examination was higher than the detection rate (28.79%) for one-time examination. The false negative rate of one-time and two-time examination in 34 individuals infested with demodicids was 44.12% and 17. 65% respectively. The study suggested that the detection rate could be improved by increasing examination time and that there was correlation between the type of skin lesion and the demodicid infestation. The results of local application and in vitro acaricidal test of 3% Man Nai Jing and 1% metronidazole cream indicated that the acaricidal effectiveness of Man Nai Jing was superior to 1% metronidazole cream and there was no significant difference in the immediate effectiveness on skin lesion for two drugs.