The probability of developing upper extremity lymphedema after surgery in breast cancer patients is 10-30%, mostly occurring within 1 year after surgery, with a few occurring several years or even decades later. Postoperative radiation therapy, history of hypertension, history of diabetes, and incisional infection are all risk factors for postoperative upper extremity lymphedema. In contrast, postoperative upper extremity functional exercises can reduce the occurrence of upper extremity lymphedema. The clinical manifestations are mild swelling, burning and heaviness, and in severe cases, elephantiasis. Prevention: Avoid weight-bearing, blood sampling, fluid transfusion, and trauma to the affected upper extremity. Treatment: Physical therapy: elevation of the affected limb, elastic bandage, massage, functional exercise. Medication: Western medicine: can be used to relieve the symptoms but not the root of the problem. Chinese medicine and Chinese medical treatment: including moxibustion, acupuncture, etc.; surgical treatment: for severe cases of edema most patients are able to improve the symptoms.