Objective To explore the correlation between homocysteine （Hcy） level and the risk of breast cancer，and try to find a new method to reduce the risk factors and benefit for treatment of breast cancer. Methods From January2010 to December 2012， 245 cases of breast cancer （breast cancer group）， 109 cases of benign breast tumor （benign breast tumor group）， and 78 cases of healthy women （healthy control group） in the Sichuan Provincial People’s Hospital， who were in accordance with the inclusion criteria， were analyzed retrospectively. The difference of Hcy level was compared among three groups. Meanwhile the relation between Hcy level and patients’s age， blood glucose， serum creatinine， estrogen receptor （ER）， progesterone receptor （PR）， Ki-67 （%）， tumor diameter， or axillary lymph node status was analyzed.Results ① The Hcy level was significantly different among the breast cancer group， benign breast tumor group， and healthy control group （P＜0.001）. The Hcy level of the breast cancer group was significantly higher than those of the benignbreast tumor group （P＜0.001） or healthy control group （P＜0.001）， but the Hcy level was not significantly different bet-ween the benign breast tumor group and healthy control group （P=0.082） . ② The Hcy levels of different types of the breastcancer （type of Luminal A， Luminal B， Her-2， and triple negative） were significantly higher than those of the benign breast tumor group （except for Her-2 type， P＜0.05） or healthy control group （P＜0.05）. ③Plasma Hcy level of the patients with benign and malignant breast tumor was positively correlated with age （r=0.197， P=0.004） or serum creatinine level （r=0.381， P＜0.001）， but not correlated with blood glucose （r=0.023， P=0.668）. ④Plasma Hcy level of the patients with malignant breast tumor was positively correlated with age （r=0.267， P=0.007） or serum creatinine level （r=0.341， P＜0.001）， but not correlated with blood glucose （r=-0.005， P=0.935）， tumor diameter （r=-0.049， P=0.443）， axillary lymph node status （r=-0.006， P=0.921）， or Ki-67 （%） （rs=-0.029， P=0.650）. Conclusions Plasma Hcy level of breast cancer patient is abnormally elevated， and it may have some relation with the occurrence of breast cancer.