Abstract: Objective To inquire into the effect of air pollution on microecology of upper respiratory tract and provide scientific basis for microecological prevention and treatment.Methods According to air monitoring material,the children lived in heavy pollution area and light pollution area were randomly sampled in 2000 and 2002.Bacteria floras of children oral and pharynx were measured.Aerobic bacteria were determined with blood agar media and EMB agar,anaerobe bacteria with anaerobic jar and counting,determine.Results There were difference between light and heavy pollution areas in the distribution of bacteria flora of pharynx.The superior bacteria floras in back wall of pharynx of children lived in light area were neisseria(85.6%),peptosueptococcus(54.4%),and α-streptococcus(42.2%) and the superior bacteria floras of students in heavy area were successively neisseria(90.1%),streptococcus pneumoniae(50.6%) and veillonela(48.1%).There were significant differences between light and heavy pollution areas about streptococcus pneumoniae and α-streptococcus(P<0.01),the amount of α-streptococcus of children decreased in heavy area.The type of bacteria of children in heavy area was 24,which higher than that in light area(17).Densities of aerobe and anaerobe bacteria in back wall of pharynx of children lived in heavy air pollution area were higher than that of children lived in light air pollution area(P<0.01).Besides,positive rate of condition pathogenic bacteria of children in heavy area was higher than that in light area(P<0.01).Conclusion Air pollution could change the balance of bacteria floras of upper respiratory tract.The decreas of α-streptococcus resulted in the increas of abnormal bacteria floras,which raised the susceptibility of respiratory disease.