Objective To observe the expression of aquaporin 4(AQP4) and the ultramicrostructure change of blood-brain barrier in human contusion brain tissue at different time points and investigate the mechanism of brain edema formation. Methods 60 cases brain contusion tissue (observation group) and 10 cases normal non-functional brain tissues (control group) were collected. The expression of AQP4 at different time point was detected by immunity histochemistry and image analytical technique at 2~72 h after injury,brain water contents, BBB index and ultramicrostructure were observed at the same time point. Results Compared with the normal control group, AQP4 expression increased in observation group at 2 h (P<0.05), obviously increased at 6 h、8 h、12 h (P<0.01), reached peak at 24~72 h(P<0.01). The change of AQP4 expression and brain water content had same tendency(r=0.912,P<0.01) which also was displayed between BBB index and brain water content(r=0.877,P<0.01). The change of AQP4 expression and BBB index had significant positive correlation(r=0.908,P<0.01). Blood-brain barrier structure changed early after injury, and then destroyed, severely damaged at 24 h, 72 h. Conclusions The expression of AQP4 and the permeability of BBB significantly increased after brain contusion which suggesting AQP4 may play an important role in the brain edema formation after brain contusion.