Objective To study the expression of human epidermal growth factor receptor-3 （HER-3） in breast cancer patients and analyze the relation between its expression and the clinical pathology of breast cancer. Methods The complete data of 139 female breast cancer patients underwent operation from January 2006 to October 2006 in this hospital were collected，who were without preoperative chemotherapy and radiation therapy，but with postoperative endo-crine therapies. HER-3 expression in the breast cancer tissues was detected by immunohistochemistry. Information on histological grading，tumor diameter，lymph node metastasis，and telephone number were obtained from their medical records. The relation between indication and HER-3 expression was analyzed. Results ①The positive expression of HER-3 in the breast cancer tissues was 30.2% （42/139）；②The expression of HER-3 was unrelated to the age of patient with breast cancer （r=0.030，P=0.721）；③HER-3 expression was a positive related to the tumor diameter （r=0.176，P=0.038）， lymph node metastasis （r=0.205，P=0.016），or histological grading （r=0.197，P=0.020），which was a negative related to the five-year survival rate （r=-0.254，P=0.003）. Conclusion Detection of HER-3 expression in breast cancer tissues might be a clinical significance for the early diagnosis/treatment，medication，and prognosis of the tumors as well as research and development of new drug.