Background:There are limited data on etiology of viral pneumonia under the impact of COVID-19 pandemic. We aimed to investigate the changes of viral pneumonia before and after COVID-19 pandemic among patients diagnosed with pneumonia. Methods:This is a single-center retrospective study. Patients hospitalized with pneumonia during January 1,2016 and Dec 31,2021 in West China Hospital were included and divided into pre- and post-COVID-19 groups according to the point of COVID-19 outbreak in China which was December 8,2019. Results of the 13 viral nucleic acid tests were compared between the two groups. Results:5,928 patients were analyzed,3,945 in the pre-COVID-19 group while 1,983 in the post-COVID-19. Respiratory viral nucleic acid screening proportion was riseing after COVID-19 (14.8％ VS 22.8％).But the positive rate of post-COVID-19 total virus and Influenza virus had decreased 23.3% and 18.3%, respectively,p＜0.05. The top three viral pneumonia were InfAH1N1(2009),Human Rhinovirus,Human Adenovirus before COVID-19, while HRV, Human Parainfluenza virus, Human Respiratory Syncytial virus after COVID-19 pandemic. Notebly,InfAH1N1(2009) pneumonia decreased to 0％ after the pandemic. Conclusions:Proportion of viral pneumonia has significantly decreased under the impact of COVID-19 pneumonia and the incidence of InfAH1N1(2009) pneumonia is almost 0.