Fatigue after radiotherapy for lung cancer can usually be recovered in 1~3 months, which should be analyzed according to the actual situation and cannot be generalized. Fatigue is a common adverse drug reaction after radiotherapy, and the recovery period is mostly in 1~3 months, but there is no uniform recovery time due to the different physical quality, tumor type, tumor staging, and dosage of radiotherapy of each patient. The vast majority of lung cancer radiotherapy patients will recover effectively from the whole lung effects, including radiotherapy damage, within 1~2 months after the end of radiotherapy. If the lung cancer radiotherapy is more extensive and the dose is higher, the recovery time may be slightly longer, usually taking about 3 months. It is suggested that patients need to strengthen the nutrition in the period of time after the radiotherapy is finished, and follow the doctor’s instructions for regular rechecking, so as to facilitate the recovery of the disease.