The role of CyclinD1 and estrogen receptor (ER) in the process of proliferation and metastasis of breast neoplasm and their relationship were studied. The expression levels of CyclinD1 and ER in the tissue samples were detected by using flow cytometry and L SAB immunohistochemistry staining, respectively. The results showed that CyclinD1 and ER expression levels in breast cancer were significantly higher than in benign breast neoplasm (P < 0.05). The CyclinD1 expression levels in stage I was much lower than in stages II, III, IV (P < 0.05). The positive rate of ER was not related with tumor size, lymph node metastasis and TNM stage (P > 0.05), but the CyclinD1 expression level in ER (+) group was significantly higher than in ER (-) group (P < 0.05). It was concluded that CyclinD1 expression level might be obviously related with the proliferation and metastasis of breast neoplasm and ER.