Objective To investigate the possible presence of radiation brain injury (RBI) in vascular injury and blood-brain barrier (BBB) damage.Methods Seventy 8 weeks old male BALB/C mice were randomly divided into irradiation group and control group;mice in the two groups received whole-brain exposure with a single dose of 10 Gy irradiation or sham irradiation.Tissue samples were taken 1,7,30,90 and 180 days after irradiation (7 mice in each time point per group);HE staining was used to observe the microvascular morphology and density changes;immune-fluorescence staining was used to visualize the differential expressions of factor Ⅷ related antigen (vWF) and zonulaoccludens-1 (ZO-1).Results Micro-vascular disorders began to appear from the first day of irradiation,deteriorating with time extension gradually.After the X-ray irradiation exposure,the protein expressions of vWF and ZO-1 in the irradiation group were significantly decreased as compared with those in the control group 1,7,30,90 and 180 days after irradiation (vWF:23.17±2.93 vs 15.80±2.39,21.25±2.33 vs 11.60±2.3,19.78±2.16 vs 8.20±1.64,17.21±3.31 vs 6.00±2.12 and 16.98±1.92 vs 3.80±2.59;ZO1:26.17±3.31 vs 15.40±1.82,23.20±2.93 vs 12.00±1.58,20.88±2.20 vs 9.10±2.55,18.32±1.87 vs 6.20±1.92 and 17.50±1.91 vs 2.40±1.52,P＜0.05);besides,the decreased expression ofvWF and ZO-1 in the irradiation group showed a time-depended manner,with significant differences between each two time points (P＜0.05).Conclusion X-rays may induce persistent micro-vascular injury and destroyed BBB tight junctions,which may be closely related to the occurrence and development of RBI.