Background Epidemiological surveys showed that the types of bacteria are different in the conjunvical sac from different nationalities,which possibly is associated with living environment.To characterize the types of conjunctival bacteria involved is important for the prevention and treatment of infectious eye diseases.Objective The present survey was to obtain data about bacterial species in the conjunctival sac in the Tibetan minority population aged over 40 years old and compared with the matched Han nationality population.Methods The standardized training and protocol were performed before this survey.A total of 290 eyes of 145 individuals from the Tibetan minority and 346 eyes of 173 subjects from the Han nationality were enrolled in this study in Ganzi Autonomous Prefecture,who had received questionnaire surveys and ophthalmological examinations.The secretion of the inferior palpebral conjunctival sac was embrocated and inoculated and grown on blood plates for 48-72 hours.The bacteria were isolated and identified.This study was approved by the Medical Ethic Committee of the Sichuan People Hospital.Oral informed consent was obtained from the subjects.Results No significant differences were seen in the constituent ratio of the gender as well as the age between the Tibetan minority and Han nationality in this study (x2 =0.987,P=0.3202;t=1.142,P=0.254).There was a significant difference in the proportions of farmers and herdsmen between the two groups(x2 =8.557,P =0.000).The positive rate of bacterial cultivation in Tibetan individuals was 50.74％,showing a statistically significant decrease in comparison with the Han people(60.4％)(x2=6.042,P=0.014).There was no statistical difference in the multiple bacterial species between the two groups (11.0％ in Tibetan,11.6％ in Han people)(x2 =0.0271,P =0.869).The rate of staphylococcus epidemics was 26.6％ in the Tibetan minority and that of Han population was 33.2％,without a significant difference between them (x2 =3.350,P=0.060).No significant difference was seen in the ratio of corynbacterium infection between the two population(15.9％ vs.17.3％)(x2 =0.248,P =0.618).Conclusions The ratio of bacterial cultivation in Tibetans is statistically lower than that of the Han people.The types and distribution of bacteria are similar in the Tibetan and Han nationality.