Abstract: Objective To search for the mechanism of ³²P-colloid perfusion therapy in the animalmodels of chronic maxillary sinusitis. Methods ³²P-colloid were injected into the male sheep maxillary sinuses of the animal-models of chronic maxillary sinusitis in different dosage group. The changes of bacteria and mucosael pathomorphology were observed by periodic germicuhure and pathology in 1, 3, 6 months after injection. Results After ³²P-colloid perfusion therapy, the amounts of bacterial species and chronic phlogistic cells were remarkable reduced, and the structure of cilia cells did not change. The curable rate was 83.3% in 6 months. There were remarkable difference in groups. Conclusions ³²P-colloid was provided with antibiosis and ruducing chronic phlogistic responses. We had found the optimal dose of ³²P-colloid perfusion in the maxillary sinuses through the study. The curable rate of single dose of ³²P-colloid perfusion in the maxillary sinuses was higher than other therapy, ³²P-colloid perfusion was simple and convenient. There was high selectivity of ³²P in the target organ, when there was no effect on other important organs through radiobiological measurement.