Objective To study the neuroprotective effects of neuregulin-1β (NRG-1β) on the nervous behavioral function, cerebral infarction volume, brain water content(BWC), neuronal apoptosis and aquaporin4(AQP-4) expression in astrocytes after cerebral ischemic reperfusion and the related mechanism in mice. Methods Intraluminal thread methods were applied to establish the middle cerebral artery occlusion reperfusion models in the mice. Neuregulin-1β (2μg / kg) was injected into the internal carotid artery for treatment. The nervous behavioral function was evaluated with Bederson’s test. The cerebral infarction volume was observed with tetrazolium chloride staining. The BWC was measured by drywet weight comparing. The apoptosis positive cells were counted by immunofluorescence assay. The expression of AQP-4 was determined by immunohistochemical assay. Results Nervous behavioral malfunction appeared in all the mice with left middle cerebral artery occlusion and/or reperfusion. The infarction focus showed in the ischemic hemisphere after the injury. The BWC, the number of neuronal apoptosis cells and AQP-4 expression in astrocytes were higher than those in the sham group. In the NRG-1β treatment group, the nervous behavioral function was improved 24 hours after ischemia, the number of apoptosis positive cells reduced and the infarction volume decreased significantly compared with the control group(P<0.05). The BWC and AQP-4 expression in astrocytes showed no significant difference compared with the control group(P>0.05). In the groups of reperfusion for 22,46 and 70 hours,the five indexes mentioned above were significantly different from those in the corresponding control groups(P<0.05). Conclusion NRG-1β may reduce cerebral edema and infarction volume and improve the nervous behavioral functio