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Objective: To understand the clinical and epidemiological characteristics of influenza virus and respiratory syncytial virus (RSV) infection in hospitalized children aged <5 years in Changzhou, Jiangsu Province, and compare their severity. Methods: Children aged <5 years and hospitalized for acute respiratory infections in Changzhou Children's Hospital from January 2024 to January 2025 were included, the information collection was conducted, multi-pathogen testing was carried out by fluorescent quantitative PCR, and χ² test was used to compare the socio-demographic and clinical characteristics of children infected with influenza virus and RSV. Multivariate logistic regression analysis was then used to evaluate the association of severe acute respiratory infection (SARI) and severe respiratory infection with influenza virus and RSV. Results: A total of 1 946 cases were included, with 147 cases (7.6%) being infected with influenza virus and 371 cases(19.1%) being infected with RSV. The RSV infection rate (28.2%) was significantly higher than that of influenza virus infection (7.5%) in the children under 1 year old. Both influenza virus and RSV infection mainly occurred in winter and spring, with the incidence of RSV infection exhibiting greater fluctuation. Compared with influenza virus infection, children with RSV infection exhibited significantly higher proportions of wheezing and asthma, as well as difficulty of feeding, however, fever and rhinorrhoea occurred less frequently, the differences were significant (all P<0.05). After adjusting for age, multivariate logistic regression analyses revealed that RSV infection had higher risk for severe respiratory symptoms (aOR=2.7, 95%CI: 1.2-7.4) and SARI (aOR=2.7, 95%CI: 1.1-8.2)in age group <1 year. Furthermore, children infected with RSV were at a higher risk for severe respiratory infection in age group 1-4 years (aOR =2.9, 95%CI: 1.3-7.0). Conclusions: RSV-related respiratory infection was more severe than influenza virus infection in children under 5 years old. Children under 1 year old are at high risk for RSV infection, and further etiological surveillance is needed to reduce the risk for serious illness.