Objective To analyze the thyroid function changes among the patients with different Wagner grades of diabetic foot disease (DF), and compare the results with the diabetic patients with non-diabetic foot (NDF) for the relationship between the severity of diabetic foot and thyroid function in type 2 diabetic patients. Methods A retrospective study was carried out on 481 DF patients and 445 NDF admitted in the Department of Endocrinology of the Chinese PLA Hospital No.306 from June 2009 to June 2015. According to the Wagner ulcer grade classification scale, the DF patients were divided into 4 groups, that is, Wagner grade 1, 2, 3, and 4-5 groups. The thyroid function was determined for all the patients, and the results were statistically analyzed among the groups by SPSS 21.0. Results The DF patients had higher incidence of thyroid dysfunction than the NDF patients (17.67% vs 12.36%, χ2=5.082, P<0.05). The subclinical hypothyroidism and euthyroid sick syndrome (ESS）were common in both the NDF and DF groups (6.07% and 8.73%). Significant differences were seen in the levels of three triiodothyronine (TT3), total thyroxine (TT4), three free triiodothyronine (FT3) between the DF and NDF groups (P<0.01). With the increase of Wagner grade, the levels of TT3 and FT3 became lower in the DF patients (P<0.01), and the percentage of ESS became higher (2.00%, 2.55%, 9.24% and 18.33% respectively for the 4 Wagner grade groups, t=24.455, P<0.05). The diabetic patients with ESS stayed in hospital longer than the others, but there was no statistical significance. Logistic regression analysis indicated that gender, length of hospital stay, high sensitivity C-reactive protein, and TT4 were the independent risk factors for DF (OR=2.938,1.178, and 1.222,1.047;P<0.01), but albumin, FT3 and 2-hour postprandial glucose level were the protective factors for DF (OR=0.881, 0.899 and 0.406; P<0.01). Conclusion There is higher incidence of ESS in DF patients, especially in those with Wagner grade 3 and above. Thyroid function test is helpful to evaluate the DF severity, and estimate the prognosis.