Abstract: Background and purpose: Significant difference exists in clinical target volume (CTV) delineation of postoperative radiotherapy for breast cancer internationally. It is necessary to have a consensus in single cancer center. Methods: We chose two typical breast cancer patients who treated in Fudan University Shanghai Cancer Center. One had conservative breast surgery and the other had modified mastectomy. Simulation computed tomography (CT) scan was used for these two patients, and data were transmitted to Varian treatment planning system. Results: We reviewed American and European consensus on breast cancer target volume delineation and the definitions of international phase 3 clinical trials. Combined with our own clinical practice, CTVs of breast, tumor bed, chest wall and regional lymph nodes were defined after many discussions by specialists. CTVs were delineated by one physician and modified by all participating experts. Conclusion: Consensus on early stage breast cancer target delineation was made in our center. This will benefit our clinical practice, teaching and research.