Abstract: Objective To investigate the correlation between thyroid function and degree of depression in patients with depression. Methods A total of 108 cases with depression were continuously collected and were divided into a study group（combined with hypothyroidism,n=31）and a control group（not combined with hypothyroidism,n=77）.Hamilton depression rating scale（HAMD）score,difference in serum thyroid hormone concentration and severity of depression were compared between the two groups,and the correlation between HAMD scores and serum thyroid hormone concentration were analyzed. Results HAMD score in the study group was significantly higher than that of the control group（28.45 °5.39 vs.22.79 °4.67,P＜0.01）.Serum triiodothyronine（T₃）,thyroxine（T₄）,free triiodothyronine（FT₃）and free thyroxine（FT₄）concentrations in the study group were significantly lower than those in the control group（P＜0.05 or P＜0.01）,and serum thyroid-stimulating hormone（TSH）concentration was significantly higher than that in the control group（P＜0.01）.Correlation analysis showed that HAMD score of depressed patients was negatively correlated with serum T₃（r=-0.269,P＜0.05）,T₄（r=-0.331,P＜0.05）and FT₄（r=-0.427,P＜0.01）concentrations,and positively correlated with serum TSH concentrations（r=0.459,P＜0.01）.Conclusions The severity of depression is closely related to thyroid function in patients with depression,which requires comprehensive treatment.