【Abstract】 Objective To explore the correlation between serum thyroid hormone levels and renal damage in patients with type 2 diabetic nephropathy. Methods 155 patients with type 2 diabetes mellitus admitted to our hospital from January 2013 to March 2018 were selected, including 65 simple type 2 diabetes (the diabetes group) and 90 type 2 diabetic nephropathy (the diabetic nephropathy group). 70 healthy people admitted to our hospital for physical examination during the same period were selected as the control group. The thyroid hormone levels ［free triiodothyronine (FT3), free thyroxine (FT4), thyroid stimulating hormone (TSH)］and urine protein levels ［microalbuminuria (mALB), 24h urine protein］and cystatin C (CysC) were assessed and compared before treatment among groups, and the Spearman correlation analysis was used to analyze the correlation between the levels of FT3, FT4 and TSH and the levels of mALB, 24h urinary protein and CysC. Results There were differences in the levels of FT3 and TSH among the three groups (P＜0.05). There was no significant difference in FT4 level (P＞0.05). The FT3 level in the three groups showed difference (P＜0.05). The TSH level in the diabetic nephropathy group was significantly higher than that in the diabetes group and the control group (P＜0.05). There were differences in the levels of mALB,24h urinary protein and CysC among the three groups (P＜0.05), and the three levels in the diabetic nephropathy group were significantly higher than those in the diabetic group and the control group (P＜0.05). The FT3 level was negatively correlated with the levels of mALB, 24h urinary protein and CysC in the diabetic nephropathy group (P＜0.05). Conclusion Serum FT3 level was negatively correlated with levels of mALB, 24h urinary protein and CysC in patients with diabetic nephropathy, and serum FT3 level may reflect renal damage to some extent.