Abstract: Objective To explore the pathologic changes in trachea of rats exposed to air pollutants.Methods Eighty specific pathogens free(SPF) Wistar rats(180-200 g of weight) were randomly divided into control group and 3 treated groups(low,moderate,and high dose group).The rats in treated groups were exposed to total suspended particulates collected in industrial and traffic areas with portable sampler for particulate mass 2.5 μmin diameter(PM_2.5) of 7.15,15 or 30 mg in 0.85% sodium chloride(NaCl) of 1ml by intratracheal instillation,and then were exposed to sulfur dioxide of 32,20,16 mg/m³ and nitrogen dioxide of 10,8,5 mg/m³ statically 4 hours per day for 7 days,respectively.One milliliter of 0.85% NaCl was instilled and general air was inhaled by the rats in control group.The changes of ultramicroscopic structure in trachea were observed under electron microscope.Results The adhesion,disturbance,lodge,and squamous metaplasia of cilia in tracheal epithelium and vacuolar degeneration in epithelium cells were observed.And the neonate ciliate epithelium was also observed.Conclusion Air pollutants may induce the decrease and loss of swing function,and the obstruction of discharging function of cilia in trachea of rats.