Objective. The aim of this study was to establish the standardization of syndrome differentiation of operative breast cancer treated with Traditional Chinese Medicine (TCM) by the modified Delphi method. Method. A literature search for standardization of syndrome differentiation of operative breast cancer was conducted and eligible articles were identified in indexed databases from 1982 to 2013. We carried out two rounds of investigation between March and October 2013 and organized 20 experts who focused on TCM or integrative medicine in breast cancer research. Experts' judgments were collected via posted questionnaires or e-mail. A final evaluation was carried out after the end of both rounds. Result. The response ratio of the 1st round investigation reached 100%, and two experts were excluded due to the uncompleted questionnaire. The 2nd round investigation was completed by 18 experts in the 1st round panel board. In both rounds, the experts agreed that the stage of breast cancer defined by TCM could be divided into the perioperation period, the perichemotherapy period, the periradiotherapy period, and the consolidation period. Conclusion. We identified the feasibility and reasonability to establish the standardization of syndrome differentiation of operative breast cancer. According to the suggestions from experts in our Delphi study, we preliminarily established the TCM standard of syndrome differentiation based on different treatment stages of operative breast cancer. Copyright © 2015 Qianqian Guo and Qianjun Chen.