OBJECTIVE：To investigate the effects of Biyuanshu （BYS）oral solution on IFN-γ of chronic rhinosinusitis （CRS）model mice ，and to investigate its potential mechanism on the basis of B 7-H1/PD-1 immune checkpoint. METHODS ：Male C57 mice were randomly divided into normal group ，sham operation group ，chemical medicine control group （clarithromycin，103 mg/kg），BYS low-dose ，medium-dose and high-dose groups （BYS oral solution ，3.1，6.2，12.4 mL/kg），with 20 mice in each group. Except for normal group without any treatment ，other mice were all open maxillary sinus ，sham operation group was not filled with sponge with bacteria ，while model group and administration groups were filled with sponge with bacteria to induce CRS model. Since 8th week after modeling ，normal group ，sham operation group and model group were given normal saline 0.2 mL intragastrically，administration groups were given relevant medicine intragastrically ，once a day ，for consecutive 14 d. The nasal symptoms and general condition of mice were observed ，and the pathological changes of mice ’s nasal sinus mucosa were observed by HE staining ；qRT-PCR was used to measure the mRNA expression of IFN-γ，B7-H1 and PD- 1 in nasal sinus mucosa of mice. RESULTS：The normal group and sham operation group had no abnormal in nose ，and the epithelium and cilia of the nasal sinus mucosa were intact ；there was no significant difference f8y3j0127@163.com in the relative mRNA expression of IFN-γ，B7-H1 and PD- 1 between 2 groups（P＞0.05）. In model group ，the mice were found to have runny n ose，frequent scratching and sneezing ，a small amount of yellow secretion in the nasal cavity ，and serious depilation ；the nasal sinus mucosa was seriously damaged ，cilia was exfoliated ，and the gland in the submucosa was hyperplasia ，lymphocyte infiltration was also found ；the relative mRNA expression of IFN-γ，B7-H1 and PD- 1 were significantly increased compared with normal group （P＜0.01）. Compared with model group，the nasal symptoms ，general condition and pathological changes of the nasal sinuses in each administration group were improved in varying degrees ；the relative mRNA expression of IFN-γ and B7-H1 in chemical medicine control group ，BYS medium-dose and high-dose groups ，as well as the relative mRNA expression of PD- 1 in administration groups were decreased significantly；above indexes of BYS medium-dose and high-dose groups were significantly lower than BYS low-dose group ，while relative mRNA expression of IFN-γ in BYS high-dose group were significantly higher than BYS medium-dose group. The relative mRNA expression of IFN-γ in BYS low-dose and medium-dose groups，the relative mRNA expression of B 7-H1 in BYS low-dose group，the relative mRNA expression of PD- 1 in BYS groups were significantly higher than chemical medicine control group ； mRNA expression of IFN-γ in BYS high-dose group was significantly higher than chemical medicine control group（P＜0.05 or P＜ 0.01）. Above indexes of BYS medium-dose group were similar to those of chemical medicine control group （P＞0.05）. CONCLUSIONS：BYS oral solution can improve chronic inflammation in nasal sinus mucosa of mice ，the mechanism of which may be associated with intervening mRNA overexpression of B 7-H1/PD-1 by inhibiting mRNA expression of IFN-γ.