Abstract: Objective　To explore the possibility for the induction of pneumocystis carinii pneumonia(PCP) in rats by dexamethasone.Methods　Forty female SD rats were randomly divided into experimental group（n=20）and control group（n=20）.Experimental group was injected subcutaneously with dexamethasone twice a week and control group was not processed.The pathogen and condition of infection were examined at 3 weeks interval. Results　Experimental group appeared clinical syndromes.The peumocystis carinii cysts and trophozoites had been found in the lung imprints and precipitate of bronchoalveolar lavage fluid since the 6th week,while no peumocystis carinii cysts and trophozoites could be found in the lung imprints and bronchoalveolar lavage fluid of control group.Conclusion　PCP rat model was successfully established by inducement of dexamethasone.