Objective: To explore the dynamic changes in the process of radiation-induced pulmonary fibrosis of B10 cells. Method: 30 C57BL/6 mice , 6-8 weeks old, were randomly divided into non-irradiated (Control) group, 2 days after irradiation (IR2d), 14 days after irradiation (IR14d), 3 month after irradiation (IR3m) and 5 month after irradiation (IR5m) group. The radiation-induced pulmonary fibrosis model was established by using ionizing radiation. Hematoxylin-eosin (HE) staining and Masson staining were used to observe the pathological changes of lung tissue, and the expression of α-SMA was observed by immunohistochemistry. Flow cytometry was used to detect the infiltration changes of B10 cells in lung tissues and spleens in the RIPF model. Results: 1. The lung tissues of mice showed inflammatory response in the early stage after chest irradiation. Furthermore, the alveolar structure destruction and interstitial filling began to appear 3m after irradiation, and a large amount of collagen was filled 5m after irradiation. The expression of α-SMA was significantly higher than that of the Control group, and pulmonary fibrosis was more severe, which could be seen from IF results. 2. The proportion of B10 cells in lung tissue was significantly increased at 2d and 14d after chest irradiation compared with the non-irradiated group, while IR3m was significantly lower than IR2d, B10 cells in the spleens began to increase at IR2d, and reached a peak at IR14d, and IR3m was significantly lower than IR2d and IR14d. Conclusion: There were B10 cells infiltration in the process of radioactive pulmonary fibrosis, with a trend of early increase and late decrease.