Abstract: Objective To investigate the relation between breast cancer and thyroid carcinoma.Methods Our study is a retrospective study including 8857 female patients in our hospital.Of these patients,650 patients suffered from breast cancer,the rest did not.There were 14 thyroid carcinoma in the group of breast cancer,42 thyroid carcinoma in the other group.Results The incidence of thyroid carcinoma was significantly higher in the group of breast cancer(2.15%)than that in the group without breast cancer(0.51%)(P＜0.05).There were no apparently statistical difference in age,mean size of tumor,extracapsular invasion,nodal involvement and pathologic type between two groups.(P＞0.05)Conclusions The patients with breast cancer have a higher incidence of thyroid carcinoma than the patients without.Ultrasonic and a fine needle aspiration by ultrasonic guidance should be routine examination.