The study was designed to evaluate the effect of ulinastatin on the permeability of the blood-brain barrier in rats with global cerebral ischemia/reperfusion injury using MRI. A total of 108 Wistar rats (240 g–280g) were randomly divided into three groups (n=36): sham group (S group), global cerebral ischemia/reperfusion model group (GCI/R group) and 10,000U/kg ulinastatin intervention group (U group). Fifty-four Wistar rats were used for MRI, and the rest were used for Evans Blue(EB)analysis. We used the Pulsinelli four-vessel occlusion (4-VO) model of global cerebral ischemia/reperfusion to investigate the integrity of the blood-brain barrier with Evans Blue (EB) staining at 15min after ischemia and at 6h (n=6), 24h (n=6), and 48h (n=6) after reperfusion to assess blood-brain barrier permeability with MRI. In the ulinastatin treatment group, the area of EB staining was significantly smaller, the exudation of EB decreased significantly after cerebral ischemia/reperfusion at 6h, 24h, 48h, compared to the model group at corresponding time points (P<0.05) but increased compared to the sham group. The model group exhibited significantly highlighted regions of Gd-DTPA after post-contrast at the corresponding areas and time points compared with the sham group (P<0.05). The highlighted regions of Gd-DTPA in the ulinastatin treatment group were significantly higher compared with those of the sham group but lower when compared with those of the model group (P<0.05). The integrity of the blood-brain barrier after cerebral ischemia/reperfusion injury was damaged. Ulinastatin could significantly improve the permeability of the blood-brain barrier after cerebral ischemia/reperfusion injury in rats.