Objective To assess the current practice of postmastectomy radiotherapy (PMRT) in mainland China and to evaluate the improvement in the past six years. Methods A questionnaire on the indications and techniques for PMRT for breast cancer was delivered to all radiotherapy centers of mainland China in 2010 survey, and the results were analyzed and compared with those in 2004 survey. The Fisher′s exact test was used. Results Compared to 29.4%(210/275) in 2004, 396 of the 952(41.6%) surveyed centers had performed PMRT. The median interval between surgery and PMRT was increased from 6 weeks to 12 weeks during the past 6 years. Adjuvant chemotherapy followed by PMRT was the most common combination in 73.5% of the responding centers in 2010 other than"Sandwich"(71.7%) sequence of chemotherapy and PMRT in 2004. PMRT was only performed for T₃ or Stage Ⅲ tumors and/or ≥ 4 positive lymph nodes (LN+) in 7.1% centers in 2004 and in 29.5% centers in 2010 surveys, respectively. The use of PMRT for T_1－2N₀ breast cancer, T_1－2N₀ with tumors located in the center or inner quadrant, and stage T₁-T₂ and one to three LN+ was decreased from 11.9%, 63.8%, and 87.6% in 2004 to 1.5%, 19.7%, and 62.1% in 2010, respectively (all P=0.000). The chest wall and the supraclavicular region were the most common radiation targets, which were used in 97.0% and 97.0% in 2010, similar to 97.1% and 96.2% in 2004.Irradiation to the inner mammary area and axillary fossa decreased from 85.2% and 74.8% in 2004 to 39.1% and 50.5% in 2010.The boost to the chest wall was more based on the scar,increasing from 9.0% in 2004 to 75.0% in 2010. Conclusions There are a high level of compliance of the practices with current guideline and continuing improvement of PMRT for breast cancer in mainland China. But it needs further improvement.