Abstract： In recent years， the theory of collateral diseases has been widely applied in the clinical diagnosis and treatment of tumor diseases and various difficult and complicated conditions. Upper extremity complications caused by breast cancer surgery and postoperative radiotherapy and chemotherapy， including axillary web syndrome， upper extremity lymphedema， and radiation-induced brachial plexus injury，with symptoms of pain，motor function limitation，edema，numbness，atrophy and impediment in the affected upper extremity， all belong to the theory of collateral diseases in Chinese medicine. The exploration of the understanding of Chinese medicine on upper extremity complications after breast cancer surgery based on collateral disease theory provides a guiding ideology for the diagnosis and treatment of the disease and has certain theoretical and clinical significance.