Objective To observe the changes of PECAM-1,Bcl-2 and Bax expressed by ischemic cerebrum of adult rats after focal cerebral ischemia. Methods Middle cerebral artery occlusion (MCAO) models were made by operation with Longa suture method in Wistar rats. The expression levels of PECAM-1,Bcl-2 and Bax at the 6th,12th,18th,24th,48th,72nd hour after MCAO were detected by immunohistochemistry staining. Results The expression levels of PECAM-1,Bcl-2 and Bax in cerebrum were significantly increased after MCAO. The expression levels of Bcl-2 we、re up to the peak at the 12th hour after MCAO, while the levels of Bax and PECAM-1 were up to the peak at the 24th and 48th hour after MCAO. At the 72nd hour after MCAO, the expression levels of PECAM.1.Bcl-2 and Bax were still higher than that in the control group(all P＜0.001).Conclusions PECAM-1,Bcl-2 and Bax participate in the different pathological stages of focal cerebral ischemia.