After mastectomy, the swelling of the upper limb on the affected side is considered to be caused by the ossification of axillary blood vessels and nerves, and the loss of elasticity of the vascular beds to support the role of tissue. It is also easy to complicate deep vein thrombosis of the upper limb after surgery, especially after the surgery, the affected limb can not be used for blood collection or venous puncture, and the damage of the venous lining can also lead to the formation of venous thrombosis. Therefore, the deep vein ultrasound examination should be carried out in time, and if there is obvious thrombosis, anticoagulation treatment should be carried out in time, at the same time, the patient’s limbs should be elevated, and drugs to improve microcirculation can also be given when necessary. And after the surgery of breast malignant tumor, it is also necessary to pay attention to the prevention of this complication. For patients with combined axillary lymph node fusion enlargement, neoadjuvant therapy can also be taken before surgery.