Objective:To summarize the clinical features of children with pneumonia caused by coinfection of human adenovirus type 7 and Mycoplasma pneumoniae.Methods:A total of 36 children with pneumonia caused by coinfection of human adenovirus type 7 and Mycoplasma pneumoniae (coinfection group) diagnosed in the Wuhan Children′s Hospital from December 1, 2018 to September 1, 2019 were enrolled.Their clinical manifestations, laboratory examinations, and imaging findings were retrospectively analyzed.In the same period, 94 children with single human adenovirus type 7 infection pneumonia were selected as the single infection group.Differences between 2 groups were compared using the Student′s t-test, rank sum test and Chi- square test. Results:In the coinfection group, 25 cases were males, 11 cases were females, their mean age was 3.11 years.The main clinical manifestations included fever (97.2%) and cough (100.0%). The mean body temperature was 40.0 ℃, with the thermal peak of 4 times per day, and the mean course of fever of 11 days.The incidence of severe pneumonia was significantly higher in coinfection group (86.1%) than that of single infection group (69.1%) ( χ2=3.878, P<0.05). The common complications included myocardial damage (55.5%), heart failure (16.7%), liver function damage (25.0%), gastrointestinal bleeding (5.5%), toxic encephalopathy (11.0%), hemophagocytic syndrome (16.7%), and bronchiolitis obliterans (50.0%). The levels of cytokines like interleukin (IL)-6 [237.84(108.59, 606.36) ng/L], IL-10[31.44(12.13, 69.60) ng/L]and interferon-γ [(102.85±92.23) ng/L] were obviously elevated, and among them, IL-6 and IL-10 elevations were significantly pronounced in coinfection group than that of single infection group[148.35(57.43, 390.82); 19.67(10.96, 35.35)] ( Z=-1.984, -2.077, all P<0.05). Lung consolidation (50.0%) and pleural effusion (38.9%) were common in coinfection group, and the incidence of pleural effusion in coinfection group was significantly higher than that of single infection group (19.1%)( χ2=5.594, P<0.05). Conclusions:Most of the pneumonia caused by human adenovirus type 7 mixed Mycoplasma pneumoniae in children is severe pneumonia, which may be related to the cytokine storm.