Lung cancer is one of the most common tumors. Malnutrition is common in patients with lung cancer which is affected by reduced intake surgery and targeted drugs. They should receive nutritional assessment through Nutritional Risk Screening 2002 and patient -generated subjective global assessment. Not all cancer patients receiving chemotherapy need nutritional therapy and routine use of nutritional therapy is not recommended for lung cancer patients receiving chemotherapy with good nutritional status. Protein synthesis and catabolism are abnormal in tumor patients. For advanced lung cancer patients protein decomposition is greater than synthesis and metabolic stress factors will also increase the protein requirement. The protein requirement of lung cancer patients is recommended to be 1. 2 ~ 2. 0 g / kg·d and the target energy intake is recommended to be 25 ~ 30 kcal / kg·d . Oral nutritional supplement is the preferred nutritional therapy for lung cancer patients suitable for patients who can swallow and have normal gastrointestinal function. For lung cancer patients whose enteral nutrition can meet the normal nutritional requirements routine parenteral nutrition therapy is not recommended. When patients cannot meet their nutritional needs through enteral nutrition e. g. severe radiation esophagitis severe nausea and vomiting supplementary parenteral nutrition or total parenteral nutrition should be selected. Oral glutamine can reduce the incidence and severity of radioactive esophageal mucositis in lung cancer patients. Low sugar and high fat formula can improve blood gas analysis and respiratory function indexes in patients with chronic obstructive pulmonary disease.