Cranial magnetic resonance imaging (MRI) examinations were performed in 419 patients with type 2 diabetes mellitus (T2DM) from June to December 2016.The brain white matter lesions were defined by white matter hyperintensity (WMH) in MRI,which was detected in 380 cases (WMH group) and not detected in 39 cases (non-WMH group).The Montreal Cognitive Assessment (MoCA) was used to evaluate the cognitive function.The study showed that there were significant differences in the duration of diabetes,the proportion of hypertension,total cholesterol (TC) and MoCA scores between the two groups (all P＜0.05).The age,duration of diabetes,hypertension and glyclated hemoglobin (HbA1c) were significantly correlated with white matter lesions(OR=1.157,1.116,5.184,1.128;P＜0.05);and the white matter lesions,age,and body mass index (BMI) were significantly correlated with cognitive dysfunction in diabetic patients (OR=2.137,1.175,1.247;P＜0.05).The study result indicates that control of white matter lesions may prevent and improve cognitive dysfunction in T2DM patients.