Objective To evaluate magnetic resonance imaging (MRI) for breast-conserving surgery. Methods In this study, 52 cases of breast cancer eligible for breast-conserving surgery judged by traditional screening methods from May 2004 to December 2007 were inspected preoperatively with MRI in order to detect the cases of muhicentric breast cancer. At the same time, tumor size and invasive extent was measured accurately with enhanced magnetic resonance sequence combined with fat-suppression to determine the minimally extent of the surgical excision required. Results In the 52 cases of breast cancer patients, 3 cases of multicentric breast cancer and 49 cases of single breast cancer were diagnosed by MRI ,there were 3 cases with extensive intraductal carcinoma in the cases of single breast cancer. The primary negative margin rate was 93.6% (44/47) in the 47 cases with breast-conserving surgery. Conclusions MRI has thesuperiority to detect the muhicentric disease and the extensive intraductal carcinoma of breast cancer.Therefore MRI is useful in determining the indication and the extent of surgical excision of breast-conservingsurgery.