Objective To explore the effect of leukoaraiosis (LA) on the efficiency of the brain function network and to analyze the features of the "small world" network with graph theory method.Methods This study involved 34 LA patients from the Department of Neurology,Beijing Tiantan hospital,Capital Medical University from January 2014 to September 2015 and 23 age-and sex-matched healthy controls(NC group).All participants underwent the neurocognitive tests including M MSE,MoCA and clinical dementia rating(CDR).The subjects were divided into LA with cognitive normal group (CN) (n=11) and LA patients with vascular cognitive impairment-non dementia group(VCIND) (n=23).Functional MRI (fMRI) was employed at resting state.And then,the functional network establishment and small-world network metrics (characteristic clustering coefficient and path length) were computed using graph analytical methods.Results In the range of 0.05 ≤ Kcost ≤ 0.5,the functional networks fitted the definition of small-worldness in LA (CN),LA(VCIND) and NC groups(δ＞1).The Lambda of group LA(CN) and LA (VCIND) were smaller than that of NC group at each threshold,and more closing to 1.The gamma of group LA(CN) were higher than that of NC group at each threshold.While the gamma of group LA(VCIND)were lower than that of NC group at each threshold.The sigma of group LA(CN) were higher than that of NC group at each threshold.Conclusion The LA patients exhibit abnormal small-world network properties.And compared with HCs,small world properties in LA (CN) patients have been increased,while that in LA (VCIND) patients have been reduced,which manifested that the altered topological properties may be responsible for cognitive dysfunction in LA patients.