Objective：The conflict between thyroid hormones and breast cancer has been studied for years and the purpose was to identify the relationship between thyroid hormones and breast cancer. Methods：Peripheral blood samples of 251 participants including 114 patients with breast cancer and 137 healthy controls between April 2016 and September 2016 were collected. The levels of serum thyroid hormones（TT3，FT3，TT4，FT4，and TSH）were examined to compare the differences in thyroid function tests between the patients with breast cancer and healthy population. Results：There were statistically significant differences in BMI，serum TT3，FT3 and FT4 levels between the breast cancer group and healthy control group（P < 0.05）. The patients with breast cancer were more likely to have a higher BMI（OR=1.112，95%CI：1.021~1.211，P=0.014）and a higher serum FT4 level（OR=1.066，95%CI：1.008~1.126，P=0.025）. There were statistically significant differences in serum FT3，FT4，TSH levels between patients with and without lymph node metastasis（P < 0.05）. The breast cancer with lymph node metastasis were more likely to have a higher serum FT3 level（OR=1.440，95%CI：1.030~2.012，P=0.033）. Conclusion：Breast cancer patients seem to have higher levels of serum thyroid hormones，especially with obesity or lymph node metastasis.