To understand the epidemiological and pathogenic characteristics of hospitalized severe acute respiratory infections (SARI) in Shanghai, China. From 2015 to 2017, one Tertiary hospital and one Secondary hospital were chosen as the surveillance sites. Two respiratory tract specimens per case were collected from SARI cases aged 15 years and older. One specimen was tested for 22 respiratory pathogens by RT-PCR, and the other specimen was cultured for 6 respiratory bacteria. A total of 287 SARI cases were enrolled for sampling and lab testing. 70.73% of the cases were aged 60 years and older, with 41.46%(119/287) were positive for at least one pathogen. Influenza virus was the predominant pathogen, accounting for 17.77%(51/287) of all SARI cases. Human rhinovirus/Enterovirus and Coronavirus were both accounting for 7.32%(21/287), followed by Mycoplasma pneumoniae (5.57%, 16/287). The positive rates of parainfluenza virus, bocavirus, adenovirus, respiratory syncytial virus and human metapneumo virus were all less than 5%. Bacterial strains were identified in seven SARI cases, including Klebsiella pneumoniae (3 strains), Staphylococcus aureus (2 strains), Streptococcus pneumoniae (1 strain) and Pseudomonas aeruginosa (1 strain). Two or Three pathogens were co-detected from 40 cases, accounting for 33.61% of 119 positive cases. The most common co-detected pathogens were influenza virus and Mycoplasma pneumoniae (10 cases). Influenza cases peaked in winter-spring and summer. Mycoplasma pneumoniae peaked in winter-spring season and overlapped with influenza. The positive rates of pathogens were not significantly different between different age groups. Various respiratory pathogens can be detected from SARI cases aged 15 years and older. Influenza virus was the predominant pathogen and the co-detection of influenza virus with Mycoplasma pneumoniae the most common one.