Objective:To compare the epidemiological and clinical characteristics of influenza A (IVA) and influenza B (IVB) in children of different ages, genders and seasons from 2016 to 2019.Methods:Retrospective analysis was performed on the children who were diagnosed as infected with influenza A and B virus in the outpatient and emergency department of Shanghai Eighth People′s Hospital from 2016 to 2019, including 2388 cases of influenza A virus infection and 1 575 cases of influenza B virus infection. The age, gender, time, characteristics of onset, and common indicators of blood routine tests were compared.Results:influenza virus infection is mostly prevalent from December to March of the next year, mainly influenza A virus, with minor epidemics from August to October of the next year, and influenza B virus from April to June of the next year. Compared with influenza B virus, children with respiratory tract infection caused by influenza A virus had higher WBC count, neutrophil, lymphocyte and monocyte abnormal proportions. The incidence rate of respiratory tract infection in the group infected with IVA was significantly higher ( P<0.05), and the incidence of infection in children among different age groups was significantly different ( P<0.05). Conclusions:The proportion of leukocyte and neutrophil increased, the lymphocyte was normal or decreased, and monocyte percentage increased in influenza A patients, which are more common than in influenza B patients, but the rate of abnormal increase of WBC was more common in influenza B cases. Children infected with influenza A are more likely to have anemia and platelet abnormality, and children with respiratory tract infection caused by the two viruses have different age groups. However, there was no significant difference between male and female.