Abstract: Objective To identify the rates of breast cancer-related lymphedema （BCRL） induced by radiotherapy in patients after breast surgery and to analyze the relative risk factors contributing to BCRL.Methods A total of 92 patients with breast cancer were treated with lumpectomy or modified radical mastectomy and afterwards conformal radiotherapy in our hospital. The determination of BCRL was based on subjective symptoms felt by patients and objective signs viewed by medical personnels. FCAT-B+4 scoring system was introduced to comment patients symptoms and circumference measurement was taken at 15 cm below the acromion process and 15 cm below the olecranon in both arms. Then the actuarial rates of BCRL were calculated. Univariate analysis was performed by ChiSquare test，and multivariable analysis was undertaken by binary logistic regression. Results The actuarial rate of complaint and positive physical finding of BCRL was respectively 53.3％ and 32.6％，among which BCRL was more likely to develop in patients with advanced nodal status（41.5％ vs. 11.1％， P=0.005），patients with stage Ⅲ（52.5％ vs. 17.3％， P=0.000），and patients receiving supraclavicular irradiation（37.8％ vs.11.1％， P=0.030）. TNM stage was the independent risk factor leading to lymphedema after multivariable analysis. Conclusion BCRL is the common complication with high morbidity induced by postoperative radiotherapy.The risk factors of BCRL include advanced nodal status， late stage and supraclavicular irradiation.