Objective To observe the effect of modified Chaihu Xixin Decoction（ 柴胡细辛汤） on the cognitive function and neurological function impairment in rats with craniocerebral injury and the possible mechanism. Methods Eighty nine Sprague Dawley rats were randomly divided into sham operation group（ n = 16）

model group（ n = 18）

positive control group（ n = 18） and low dose（ n = 18） and high dose（ n = 19） of Chinese herb groups. Controlled cortical impact injury model were built in these groups except sham operation group. The day after modeling

positive control group was given 0. 45 g/（ kg·d） of Donepezil Hydrochloride Tablets

low dose of Chinese herb group was given 6. 5 g/（ kg·d） of modified Chaihu Xixin Decoction

high dose of Chinese herb group was given 13 g/（ kg·d） of Chaihu Xixin Decoction

and sham operation group and model group were given double distilled water of the same volume. Each group was treated for 4 weeks by gavage. Cognitive function（ water maze test）

modified neurological severity score（ m NSS）

brain histopathology and ultrastructure of hippocampal CA1 in these groups were compared.The expression of brain derived neurotrophic factor（ BDNF） and synaptophysin1（ SYN1） were tested. Results On day 0

day 3

and day 7 after modeling

m NSS in the all other groups were significantly increased compared with that in the sham operation group（ P < 0. 01）. On day 7 and day 28 after modeling

m NSS in the high dose of Chinese herb group was decreased compared with that in model group. At day 28 after modeling

m NSS in the low dose of Chinese herb group was also decreased compared with that in model group（ P < 0. 05 or P < 0. 01）. In water maze test

escape latency time in groups given medicines was decreased compared with that in model group（ P < 0. 05 or P <0. 01）. Injured hippocampal pathologic examination in groups given medicines was better than that in model group.The injured ultrastructure of neuron

mitochondrion and synapse in hippocampal CA1 in low and high dose of Chinese herb groups could be improved. The expression of BDNF in high dose of Chinese herb group was significantly higher than that in model group and positive control group. The expression of SYN1 in high dose of Chinese herb group was higher than that in model group（ P < 0. 01）. Conclusion Modified Chaihu Xixin Decoction could improve cognitive function and neurological function in rats with craniocerebral injury. Its mechanisms might be that Modified Chaihu Xixin Decoction could increase the expression of BDNF and SYN1 in hippocampal CA1 to promote the healing in injured neuron

as well as promote synaptic remodeling and improve ultrastructure in hippocampal CA1.