One drain or two drains are usually placed after breast cancer surgery for the following reasons: First, because there is a flap in the local area after breast cancer surgery, there may be fluid under the flap after the wound is closed, so a drain needs to be placed to drain the fluid outside; second, there may be some complications after surgery, such as bleeding or lymphatic fistula, with lymphatic fistula being more common. If no drainage tube is placed, the lymphatic fluid accumulation under the flap will affect the wound healing, so draining the fluid outside the body can promote wound healing. At the same time, the color of the drainage tube should be observed after surgery, as well as the amount of drainage. If the color of the drainage tube is yellowish and light, it is normal, but if the color of the drainage tube is white or celiac and the amount of drainage is very high, 300mL or even 500mL or more per day, it means that the patient has a lymphatic fistula and needs further treatment.