Objective To Study the expression of apo E protein changed in different wound age and position of the experimental traumatic brain injury(TBI) in rat. Methods The animal model of cerebral contusion was established by impact to the parietal lobe with a free fall weight,observed the changes of apo E in different wound age (0.5h、2h、6h、12h、24h、3d、7d、14d). The results were measured quantitatively with computer imaging analysis system. Results In cortex apo E-positive neurons definitely detected in 0.5h after brain injury, reaching the peak in 3d, then it shows the gradual decrease from 3d to 14d; In hippocampus apo E-positive neurons definitely detected in 0.5h after brain injury, reaching the peak in 3d in CA1 section and 24h in CA2～CA4. Then it shows the gradual decrease. We found the expression of apo E protein in CA1 section is stronger than others. Conclusion The location and intersity of the immunoreactivity of apo E protein changed at the different stages after TBI. These changes observed in the present study might be used for determination of injury time,early diagnosis and distinguish antemortem and postmortem brain injury in forensic medicine.