Objective To analyze the clinical characteristics of patients with influenza A virus infection complicated with pneumonia during the peak period of influenza. Methods From December 2018 to April 2019, hospitalized patients with influenza A virus infection complicated with pneumonia in the respiratory department of a hospital were classified as influenza A complicated with pneumonia group, patients only with influenza A virus infection in internal medicine outpatient department were classified as influenza A group, and the healthy physical examinees in physical examination center were classified as physical examination group, clinical manifestations and characteristics of patients were retrospectively analyzed. Results There were 57 cases in influenza A complicated with pneumonia group, 42 cases in influenza A group, and 33 in physical examination group, difference in age among three groups was significant (F=16.57, P < 0.001). The age of patients in influenza A complicated with pneumonia group was the oldest, which was (61.65±16.92) years. White blood cell (WBC) count, neutrophil percentage, C-reactive protein (CRP), procalcitonin (PCT) and serum amyloid A protein (SAA) of patients in influenza A complicated pneumonia group were higher than those of patients in influenza A group and persons in physical examination group (all P < 0.05). Cycle threshold (CT) value of influenza A virus load nucleic acid detection in patients in influenza A complicated with pneumonia group was lower than that in patients in influenza A group ([16.18±2.53] vs [19.30±4.12], t=2.100, P=0.039); correlation coefficients (r) between CT value and CRP as well as PCT in patients in influenza A complicated with pneumonia group were -0.51 and -0.55 respectively, both were negatively correlated. Conclusion Patients with influenza A virus infection are elderly people with high influenza A virus load, the increase of CRP and PCT suggests the risk of pneumonia for patients with influenza A virus infection, which can provide the basis for clinical diagnosis and treatment.