Objective To investigate the clinical significance of brain-derived neurotrophic factor (BDNF) from peripheral serum in patients of vascular cognitive impairment (VCI).Methods Forty VCI subjects (including 10 mild cognitive impairment vascular(MCI-V) and 30 vascular dementia(VD)),and the control group for the same period in 40 healthy persons.Enzyme-linked immunosorbant assay (ELISA) was used to measure the serum levels of BDNF,statistical analysis was performed.Results The peripheral serum levels of BDNF in VCI (0.175 ±0.056) ng/L were lower than those of control group (0.211 ±0.061) ng/L,and there were significant differences (t =-2.752,P ＜ 0.05).The levels of BDNF showed no significant difference between MCI and VD ((0.195 ± 0.067) ng/L vs.(0.168 ± 0.052) ng/L,t =1.310,P ＞ 0.05).But they were both significantly lower than the control group (F =4.590,P =0.013).No significant differences were observed in the levels of BDNF between subcortical small vessel dementia (0.178 ± 0.057) ng/L and big vascular dementia (0.154 ± 0.042) ng/L (t =1.278,P =0.212).Conclusion BDNF participate in pathophysiology of VCI,and the serum levels of BDNF may be a candidate marker for clinical diagnosis of VCI.But serum levels of BDNF could not reflect the severity or the type of the VCI.