Abstract: OBJECTIVE To explore the value of computed tomography（CT） in differential diagnosis of pulmonary fungal infection and pulmonary bacterial infection in lung cancer patients. METHODS A total of 86 patients with pulmonary fungal infection and pulmonary bacterial infection who were treated in Zhejiang Quhua Hospital from Jan 2019 to Apr 2020 were recruited as study subjects, including 35 cases of pulmonary fungal infection and 51 cases of pulmonary bacterial infection. The CT features of lesions, number of forms, voids, halo signs and anti-halo-signs were compared between the two groups of patients, the pathogens isolated from the two groups of patients were identified, and the species of pathogens were observed. RESULTS Among the patients with pulmonary fungal infection, there were 11（31.43%） patients who had one type of CT feature and 24（68.57%） patients who had no less than two types of CT features. Among the patients with pulmonary bacteria l infection, there were 35（68.63%） patients who had one type of CT feature and 16（31.37%） patients who had no less than two types; there were significant differences between the two groups（P＜0.05）. There were significant differences in the proportions of the patients with consolidations and the patients with mass between the pulmonary fungal infection group and the pulmonary bacterial infection group（P＜0.05）. There were significant differences in the number of mass, proportion of cavitation and proportion of consolidation manifested as air bronchial signs between the pulmonary fungal infection and the pulmonary bacterial infection group（P＜0.05）. Totally 37 strains of pathogens were isolated from the patients with pulmonary fungal infection, including 20（54.05%） strains of Aspergillus, 12（32.43%） strains of mucor and 5（13.51%） strains of other species. Totally 58 strains of pathogens were isolated from the patients with pulmonary bacterial infection, 31（53.45%） of which were gram-negative bacteria, 27（46.55%） were gram-positive bacteria. CONCLUSION The pulmonary fungal infections in the lung cancer patients are similar to the bacterial infections, but the patients with fungal infections have no less than 2 types of manifestations, high proportion of mass, low proportion of consolidation and high single rate of mass manifestations, the cavities are easily formed, and the incidence of air bronchial sign is high.