ObjectiveTo evaluate whether oral administration of Chinese tradiational medicine,Qing-Xue granula,can prevent mouse lung injury caused by thoracic radiation.Methods128 BalB/C mice were divided into 4 groups:control (C) group; radiation (R) group; radiation plus high dose Qing-Xue granula (H) group and radiation plus median dose Qing-Xue granula ( M ) group.The H and M groups were fed 0.64 g and 0.32 g of Qing-Xue granula dissolved in 0.5 nl anline once daily for two months,which were 4 and 2 times of human dosage,respectively.Whole thorax radiation of 12 Gy was delivered with a single ventral-dorsal field with 6 MV X-ray.Group C and group R received 21 days of 0.5 ml saline feeding.Mice were sacrificed at 1,2,4 or 6 months after radiation. Macrophage cell count of lung lavage fluid and hydroxyproline content of left lung were assayed,and the lung fibrosis was scorred according to the Ashcroft's criteria.The plasma interleukin-6 (IL-6) and vascular endothelial growth factor (VEGF) concentration were assayed with ELISA method.The One-way ANOVA was used to test the significance of any differences between groups at each time point. Results The macrophage cell number of lung lavage fluid was significantly lower in the 1st month in group M than in group R (2∶4,q =3.92,P ＜ 0.05 ),but had no significant difference between group M and C ( 1 ∶ 4,q =2.13,P＞0.05 ).The hydroxyproline content of group H was significantly lower than group R in the 1st and 6th months (q =3.62,3.54,all P ＜ 0.05 ),but still higher than group C ( q =4.09,3.72,all P ＜ 0.05 ).The fibrosis score of group H was significantly lower than group R in the 2nd,4th and 6th months (q=3.38 -4.16,all P＜0.05).The IL-6 concentration of group H was significantly lower than group R in the 1st month ( q=3.53,P＜0.05 ),but not significantly higher than group C (q =1.41,P＞0.05).The VEGF concentration was significantly higher in group R than group C since the 2nd month ( q =3.12 - 3.78,P ＜ 0.05 ).The VEGF concentration was significantly higher in group H and M than group R in the 2nd and 6th months ( q =3.08 - 3.92,all P ＜ 0.0 5 ).Conclusions Oral Chinese traditional medicine,Qing-Xue granula,could prevent radiation induced lung fibrosis in mice,especially at high dosage.The degree of elevation of VEGF in plasma was not parallel with that of lung fibrosis.