Objective To analyzed epidemiology and clinical feature of respiratory syncytial virus(RSV) in Xiamen, China, and to compare RSV infections before, during and after the COVID-19 pandemic. Methods From January 2017 to December 2023, medical records of inpatients aged under 5 years with lower respiratory infection with RSV infections were reviewed. The epidemiology and clinical features were analyzed. Results The peak of RSV epidemiology was shifted from September (pre-COVID-19) to June-September (during and post-COVID-19). The proportion of patients aged over 2 years increased during and post-COVID-19 period (29.5% and 35.2% vs 14.9%, P<0.01). Compared with pre-COVID-19 period, fever was more prevalent during and post-COVID-19 period (70.5% and 76.0% vs 51.6%, P<0.01). The incidence of oxygen supplement and ventilator usage was higher in the post-COVID-19 period compared with pre-COVID-19 period (43.2% vs 28.8% and 10.4% vs 2.3%, P<0.01). Clinical characteristics across the three period by age stratified noted increased disease severity in children aged under 6 months, with higher incidence of ventilator usage and ICU admissions during the COVID-19 pandemic and post-COVID-19 period(P<0.015), while disease severity was similar in children aged over 2years across three phases. Binary logistic regression analyses for risk factors of ICU admission showed that younger age (adjusted OR 2.7,95% CI 1.9-3.8, P <0.001), tachypnea (adjusted OR 3.4,95% CI 2.2-5.4, P <0.001) were the significant independent risk factors associated with ICU admissions in RSV infection. Conclusion The COVID-19 pandemic has altered RSV epidemiology and clinical characteristics, increased severity was observed in children aged under 6 months during these periods. These findings underscore the need for continued surveillance of RSV patterns in the post-COVID-19 era and adaptive prevention strategies.