Cerebral edema is a critical complication after intravascular thrombolysis post-acute stroke. However, clinical options remained limited for treating cerebral edema after cerebral ischemia/reperfusion (I/R) injury. In the present study, astragaloside IV, a purified extract from astragalus membranaceus, was used in the focal I/R rat model, aimed to investigate its effect on the cerebral edema. We found that astragaloside IV (10 and 20 mg/kg) significantly attenuated the cerebral water content (P<0.05) and improved neurological outcomes (P<0.05) in comparison with vehicle group. Moreover, we investigate the effect of astragaloside IV on the (blood–brain barrier) BBB since cerebral edema was closely related to the permeability of the BBB. We found that the permeability of BBB was improved significantly in astragaloside IV groups compared with vehicle group via Evans blue leakage (P<0.05). This was further confirmed under the electron microscope, using lanthanum as a tracer of blood vessel permeability. Lanthanum was usually found within the blood vessel in sham group, rather than in perivascular tissues as shown in vehicle group. In drug groups, lanthanum stain was mainly restricted within the cerebral capillary, indicating the potential BBB-protective effect of astragaloside IV. Furthermore, we found that expressions of Matrix metalloproteinase-9 (MMP-9) and aquaporin 4 (AQP4) were increased in vehicle group, which were related to cerebral vasogenic edema or cytotoxic edema. The up-regulations of MMP-9 and AQP4 were inhibited significantly by astragaloside IV administration. We propose that the anti-edema potential of astragaloside IV was correlated with its regulation of MMP-9 and AQP4.