Abstract： Objective:To study the clinical characteristics of respiratory syncytial viral pneumonia in children aged 2 to 5 years, and pinpoint the risk factors of severe pneumonia, in order to establish a basis for early diagnosis.Methods:We performed a retrospective investigation of clinical data from 210 children aged 2-5 years, diagnosed with respiratory syncytial virus pneumonia and hospitalized in our institution from December 2017 to June 2023 of New Century International Children′s Hospital, Beijing. According to the severity of their illness, they were divided into mild group and severe group. The aim was to compare their general data and clinical characteristics and to analyze the risk factors of severe respiratory syncytial viral pneumonia.Results:Among 210 children infected with RSV pneumonia, the male to female ratio was 1.26∶1, with a peak body temperature of 39.35±0.68 ℃, an average course of fever was 5.98±2.20 days, and an average hospital stay of 7.16±2.29 days. RSV pneumonia occurred throughout the year, predominantly in spring and winter. Among the children affected, 26.19% had tachypnea, 22.38% had three concave sign, 77.14% had moist rales in the lungs, 42.86% had wheezing sounds, 22.86% had myocardial damage, 15.24% had diffuse panbronchiolitis. The result from the univariate analysis showed that there were statistically significant differences in preterm delivery, peak body temperature, length of hospital stay, tachypnea, wheezing, three concave sign, moist rale, wheezing sound, CRP, X-ray pulmonary shadow and diffuse panbronchiolitis between mild and severe groups ( P<0.05). Multivariate logistic regression analysis showed that moist rales and X-ray lung shadows were risk factors for severe RSV pneumonia. Conclusions:Importantly, certain clinical differences were observed between mild and severe cases of respiratory syncytial virus pneumonia in children aged 2 to 5 years. Moist rales and X-ray lung shadows are independent risk factors for severe respiratory syncytial viral pneumonia in children aged 2 to 5 years.