Abstract: Objective To investigate the death reasons for elderly inpatients with advanced lung cancer and the influencing factors on pulmonary infection. Methods A retrospective analysis was performed on 88 dead elderly patients with primary lung cancer. Results All patients were more than 65 years old. Performance status score >2 accounted for 81.82%. More than 90% of them had at least one organ metastasis. Most of them had multiple basic diseases and underwent one or more invasive operation during hospitalization. Pulmonary infection was the main complication. The prognosis was poor. 68.18% of the patients directly or indirectly died of pulmonary infection. Gram-negative bacteria were the main pathogens in patients with advanced lung cancer accompanied with fungal infection. More than three kinds of antineoplastic therapy, pleural effusion, pulmonary metastasis and long hospital stay were risk factors for pulmonary infection. Conclusion The pulmonary infection has become the most common cause of death and major complication in elderly patients with advanced lung cancer. Early detection of metastatic sites, effective treatment of pulmonary and pleural metastasis, reducing the susceptible factors and timely control of infection according to sputum culture are the main measures to improve the therapeutic efficacy in elderly patients with advanced lung cancer.