Objective:To analyze the effect of Croton leaf on ERK1/2 pathway in hippocampal of rats with cerebral ischemia-reperfusion.Methods:A total of 216 SD male rats were divided into sham operation group, model group, nimodipine group, low-dose, medium-dose and high-dose groups of croton leaf according to random nubmer table method, with 36 rats in each group. The MACO model of rats was prepared by the method of wire embolization. The high, medium and low dose groups were intragastrated with the water decoction 0.06 g/ml, 0.12 g/ml and 0.18 g/ml of Croton leaf; nimodipine group was intragastrated with nimodipine suspension 1.08 g/L; sham operation group and model group were intragastrated with equal volume of normal saline. Garcia JH score was used to conduct neurological function score, and HE staining was used to observe the morphology of hippocampal neurons after 7 days of continuous administration. Apoptosis of hippocampal CA3/DG region was detected by TUNEL assay. Western Blot was used to detect the expression of ERK1/2 and p-ERK1/2 proteins.Results:Compared with the model group at simultaneous point, the neurological function scores of low-dose, medium-dose and high-dose groups of Croton leaf increased ( P<0.01), the number of apoptotic cells decreased ( P<0.01), the expression of p-ERK1/2 / ERK1/2 [1 d: (0.22±0.03, 0.34±0.02, 0.46±0.01 vs. 0.19±0.02); 3 d: (0.38±0.02, 0.50±0.02, 0.68±0.02 vs. 0.27±0.02); 7 d: (0.29±0.03, 0.43±0.02, 0.59±0.02 vs. 0.21±0.03)] in hippocampus of the low-dose, medium-dose and high-dose groups of Croton leaf significantly increased ( P<0.01). Conclusion:Croton leaf could regulate the expression of ERK1/2 pathway protein upward, effectively improve the neural function and resist the apoptosis of hippocampal CA3/DG area of rats with cerebral ischemia-reperfusion injury.