Objective To explore the correlation between thyroid function and cognitive ability in patients with subcortical arteriosclerotic encephalopathy.Methods Montreal cognitive assessment scale (Montreal Cognitive Assessment,MoCA) was used to evaluate the cognitive function of SAE patients with normal thyroid function and hypothyroidism.And the difference in the risk factors of SAE cognitive ability in patients with different thyroid functions was analyzed.Results There were no significant differences in gender,age,risk factors of hypertension,cerebral infarction,diabetes and smoking between the two groups (P＞0.05).The levels of FT3,FT4,TSH,MoCA and ADL in patients with hypothyroidism were (2.92±0.35) pmol/L,(15.61±2.76) pmol/L,(13.05± 1.64) mU/L,(12.73±5.75) points,(45.64±25.77) points,respectively.The levels of FT3,FT4 and TSH in normal thyroid function group and MoCA,ADL scores were (4.27±0.55)pmol/L,(16.74 ± 2.35) pmol/L,(2.73 ± 0.38) mU/L,(18.15 ± 5.35) points,(62.17 ± 26.72) points,respectively.The data of the hypothyroidism group was significantly lower than thst in the normal thyroid function group,and the difference was statistically significant (t =3.591,3.012,12.753,8.967,15.442,P＜0.05).FT3 levels in SAE patients were positively correlated with MoCA score and ADL score (r=0.518,0.617,P=0.026,0.018),while there was no significant correlation between FT4 level and MoCA and ADL score (r =0.015,0.007,P =0.852,0.074).MoCA score and ADL score were negatively correlated with TSH level (r=-0.651,-0.582,P=0.016,0.005).Conclusion Thyroid function is significantly correlated with cognitive ability of SAE patients.Thyroid function may be a clinical index for patients with subcortical arteriosclerosis,and provide a basis for rational drug use in patients with subcortical arteriosclerosis.