ObjectiveTo study the effect of Wulingsan on cerebral edema after intracerebral hemorrhage （ICH） in mice and explore the treatment mechanism. MethodsThe mouse model of ICH was established by injection of collagenase into the caudate nucleus. Mice were randomly assigned into the following groups： sham， ICH， intervention before modeling with low-dose and high-dose （3.69， 11.07 g·kg^-1， respectively） Wulingsan， and intervention after modeling with high-dose Wulingsan. The modified neurological severity score （mNSS） was recorded， and the small animal MRI T2 sequential scanning was performed to measure the volume of cerebral hemorrhage after the modeling of ICH in each group. The Y-maze test， open field test， and Morris water maze test were conducted to evaluate the neurological behaviors of mice in each group. Hematoxylin-eosin staining was employed to observe the pathological changes in the brain tissue. Immunohistochemistry was employed to observe the expression of aquaporin 4 （AQP4）， neuronal nuclei （NeuN）， and glial fibrillary acidic protein （GFAP） in the brain tissue. Western blot was employed to determine the protein levels of AQP4， Claudin-5， and zonula occludens-1 （ZO-1） in the hematoma area. ResultsCompared with the sham group， the ICH group showed increases in the mNSS， the cerebral hemorrhage volume， and the escape latency in the Morris water maze test （P<0.01）， decreases in the times of touching the platform and times of entering the quadrant where the platform was located in the Morris water maze test， and reductions in the spontaneous alternation rate in the Y-maze test and the ratio of distance of center travel to total travel distance in the open field test （P<0.01）. Moreover， pathological changes such as cell disarrangement， cell space enlargement， and cell swelling were observed in the ICH group. Immunohistochemistry results showed that the ICH group had higher proportions of AQP4- and GFAP-positive cells and lower proportion of NeuN-positive cells than the sham group （P<0.01）. Compared with the sham group， the ICH group showed an up-regulated protein level of AQP4 and down-regulated protein levels of Claudin-5 and ZO-1 （P<0.01）. Compared with the ICH group， the intervention with Wulingsan decreased the mNSS， the volume of cerebral hemorrhage， and the escape latency in the Morris water maze test （P<0.05， P<0.01）， while increasing the times of touching the platform and times of entering the quadrant where the platform was located in the Morris water maze test， the spontaneous alternation rate in the Y-maze test， and the ratio of distance of center travel to total travel distance in the open field test （P<0.05， P<0.01）. Furthermore， the intervention with Wulingsan alleviated the pathological changes in the brain tissue after ICH， decreased the proportion of AQP4- and GFAP-positive cells （P<0.01）， increased the proportion of NeuN-positive cells （P<0.01）， down-regulated the protein level of AQP4 （P<0.01）， and up-regulated the protein levels of Claudin-5 and ZO-1 （P<0.01）. ConclusionThe intervention with Wulingsan could reduce the neural function score and the cerebral hemorrhage volume， up-regulate the expression of Claudin-5 and ZO-1， and down-regulate the expression of AQP4 to ameliorate the neurological function defect and cerebral edema after ICH， thereby protecting the brain.