Abstract: Objective To explore the relationship between expression thange of P-selectin after brain injury and secondary brain damage.Methods Sixty SD rats were randomized into 3 equal groups,namely the control group,mild injury group and severe injury group and animal models of brain injury were established in SD rats according to the method of Feeney.P-selectin expression in the brain tissues were determined at 6 h and l,3,and 7 days following brain injury(n=5 for each time point).Imaging analysis was performed using computerized imaging technique.Results P-selectin expression and neutrophil infiltration in the brain tissues increased significantly 6 h after brain injury(P<0.05),reaching the peak level at postoperative 24 h and then gradually decreased.Conclusion P-selectin expression and neutrophil infiltration increase significantly following brain injury,and the time course and distribution of P-selectin expression are consistent with the secondary damage of the brain,strongly suggesting the involvement of P-selectin upregulation in the secondary insult after brain injury.