Objective:To analyze the clinical characteristics of severe adenovirus pneumonia with bacterial infection in children, so as to provide clinical evidences for early diagnosis and reliable treatment.Methods:A total of 72 pediatric cases with severe adenovirus pneumonia admitted to Pediatric Intensive Care Unit at the First People′s Hospital of Chenzhou from January 2018 to August 2019 were included.The clinical features, laboratory and imaging data, efficacy of the treatments and prognosis were investigated retrospectively.Patients were divided into with bacterial infection group and without bacterial infection group.The clinical characteristics were analyzed.Results:Among the 72 children, there were 54 males and 18 females, aging from 3 months to 5 years, including 37cases with bacterial infection and 35 cases without bacterial infection.Compared with the group without bacterial infection, the group with bacterial infection had longer heat duration and hospital stay [12.0 (10.0, 18.5) days vs.10.0 (9.0, 12.0) days; 6.0(4.0, 7.0) days vs.11.0(6.5, 16.0) days, P<0.05], the incidences of diarrhea and hepatomegaly were higher[35.1% (13/37) vs.14.3%(5/35); 45.9%(17/37)vs.8.6%(3/35), P<0.05], the proportion of five lobes involved in lung imaging was higher [91.8% (34/37) vs. 57.1%(20/35), P<0.05]. The incidences of complications with respiratory failure, hemophagocytic lymphohistiocytosis, and bronchiolitis obliterans in the group with bacterial infection were significantly higher than those of without bacterial infection group ( P<0.05). Conclusion:For children under 2 years old age with severe adenovirus pneumonia, there are prolonged high fever and extensive pulmonary lesions.We should be highly alert to the combination of bacterial infection and timely anti-infection therapy.Children with severe adenovirus pneumonia with bacterial infection have severe clinical manifestations and many complications with respiratory failure, hemophagocytic lymphohistiocytosis, and bronchiolitis obliterans.