Subcutaneous effusion and flap necrosis are one of the common complications after radical breast cancer surgery. Although they do not directly threaten patients’ lives, they increase patients’ pain, mental stress, prolong hospitalization, increase patients’ financial burden, and delay postoperative chemotherapy, thus affecting patients’ overall treatment outcome. Subcutaneous effusion is a common complication after radical breast cancer surgery, and its incidence is reported to be about 10-30% in foreign literature. Subcutaneous effusion is often the main cause of flap necrosis if not treated properly. The common locations of subcutaneous effusion are under the subclavian flap, axilla and anterior chest wall under the low flap. The clinical manifestations are: 1, when a small amount of local subcutaneous effusion is present, swelling at the site of the effusion is seen, with fluctuating sensation and fluid accumulation by puncture. 2.The axillary effusion shows local fluctuating sensation, sometimes combined with swelling of upper limbs. 3.When the amount of fluid accumulation is large, a wide range of skin flaps can be seen floating. Analysis of common causes of subcutaneous effusion and corresponding measures: 1. Intraoperative lymphatic vessel destruction is too heavy. Inadequate ligation of lymphatic vessels; intraoperative electrocoagulation to close the lymphatic vessels, and postoperative crusting off, resulting in lymphatic vessel leakage and formation of subcutaneous effusion. Therefore, intraoperative large lymphatic vessels should be ligated thoroughly. In addition, combined with the preoperative clinical staging and intraoperative situation, axillary lymph node dissection is appropriate and should not be blindly expanded to cause unnecessary damage. 2. In diabetic and obese patients, the incidence of postoperative subcutaneous effusion is higher. Diabetic patients should control blood glucose at 5.6~11.2mmol/l during the perioperative period, and strengthen high protein diet after surgery. Obese patients should use the electric knife reasonably to avoid fat liquefaction, postoperative aseptic necrosis and formation of exudate. When freeing the flap, the flap near the mass should be thin. More distant areas, the flap should not be too thin to avoid affecting the blood supply, resulting in poor circulation and necrosis of the flap. 3, poor drainage. Drainage tube is too thin, improper drainage tube position, improper drainage tube side hole, failure to reasonably squeeze the drainage tube in time after surgery, resulting in blood clots blocking the lumen; postoperative negative pressure suction device leakage or negative pressure is too small; improper dressing dressing, too tight restricts breathing, affecting the local blood circulation of the flap, too loose will make the flap and chest wall fixed inaccurately, leaving a dead space. Therefore, the position of the drainage tube and the thickness of the drainage tube and the lateral hole must be correct and suitable, the negative pressure attraction must be effective, the dressing dressing should be loose and tight, and the drainage tube should be squeezed frequently after the operation to keep it unobstructed, especially important 24~48 hours after the operation. 3 ~ 4 days after surgery can be changed to observe the flap situation, but still need dressing dressing. 4, improper timing of drainage tube removal. Generally, if the drainage is smooth, the total drainage flow is less than 10ml in 24 hours, and the 2 drains can be removed in parts or all at once. The extraction time is usually 5~7 days after surgery, depending on the situation. It can be advanced by 1~2 days, and can be extended to about 10 days if necessary. After extraction, a small amount of fluid can be cured by puncture and aspiration. If the amount of drainage is still high, the drainage tube can be removed and replaced by natural drainage, and the original incision can be enlarged or another incision can be placed with rubber drainage strips. Patients with longer fluid accumulation and fibrous tissue formation in the trauma cavity should remove the fibrous tissue, keep the trauma fresh, and the local dressing with pressure can be cured. The treatment process must be strengthened with aseptic operation, and oral antibiotics can be taken to prevent infection if necessary and depending on the situation.