Coughing up blood one month after lung cancer surgery may be caused by poor postoperative recovery, lung infection and chronic inflammation. 1. Poor postoperative recovery: if patients do not pay attention to diet after surgery, and the body does not replenish the needed nutrients, it may cause slow recovery of wounds, and coughing may stimulate the local wounds to damage and bleed again. 2. Lung infection: if the patient has poor postoperative recovery, then the wound may become infected during healing, which may lead to lung infection and coughing up blood one month after the surgery. 3. Chronic inflammation: some patients need to carry out some subsequent intubation treatment after surgery, which will cause damage to the respiratory tract and pharynx, and the bronchial tubes will form chronic inflammation in the long run, thus coughing up blood one month after surgery may occur. When coughing up blood one month after lung cancer surgery, it is suggested that patients should go to the hospital in time to receive professional diagnosis from doctors, so as to clarify the cause of the disease and treat it in time.