Abstract: To investigate the expression of Nestin in the ischemic tolerance induced by focal cerebral ischemic preconditioning. Methods Cerebral ischemic preconditioning (CIP) was induced by intraluminal filament middle cerebral artery for 20 min. Middle cerebral artery occlusion (MCAO) was induced by intraluminal filament for 2h, 72h after IP. Forty five male SD rats were randomly divided into 3 groups (5 in each group): sham operation group did not receive any treatment, MCAO group only received sham surgery and 2h MCAO followed by 6h ,24h,72h reperfusion respectively,and CIP group received simple 20 min ischemic preconditioning and the same second procedure. At end of reperfusion the infarct volume was measured by TTC staining, and the expression of Nestin was detected by immunohistochemistry in each group. Results The infarct volume of CIP group was significantly less than that of MCAO (P<0.05)at 24h, 72h after reperfusion. The rate of Nestin positive cells in the brain of MCAO group was significantly lower than that in the CIP group at 24h, 72h after reperfusion (P<0.05)，meanwhile，the expressions of nestin protein in the ischemic cerebral hemispherewere analyzed with Western blotting was consistent with above-mentioned tendency.Conclusion Focal cerebral ischemic preconditioning can upregulate the expression of intermediate filament（Nestin）, which might be associated with the mechanism of BIT.