Abstract: Objective: To investigate the correlation between thyroid function and depression degree in patients with depression. Method: 108 cases with depression were continuously collected and were divided into a study group (n=31 cases, combined with hypothyroidism) and a control group (n=77 cases, not combined with hypothyroidism), Hamilton depression rating scale (HAMD) scores, difference in serum thyroid hormone concentration and severity of depression were compared between 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=0.000). Serum T3 (P=0.017), T4 (P=0.000), FT3 (P=0.005) and FT4 (P=0.000) concentrations in the study group were significantly lower than those in the control group, and serum TSH concentrations were significantly higher than that in the control group (P=0.000). Correlation analysis showed that HAMD score of depressed patients was negatively correlated with serum T4 (P=0.013) and FT4 (P=0.008) concentrations, and positively correlated with serum TSH concentrations (P=0.009). Conclusion: The severity of depression was closely related to thyroid function in patients with depression, which requires comprehensive treatment