Abstract: OBJECTIVE To explore the classification and distribution features of flu in Beijing during the flu season of the winter and the spring from 2017 to 2018. METHODS A total of 5 447 cases of adult influenza-like illness (ILI) in a "AAA" hospital during the flu outbreak were gathered. Rapid influenza screening was conducted using antigen test kit for Flu A/B (colloidal gold method), and nucleic acid was detected by real-time RT-PCR to confirm influenza and its type. SPSS19.0 statistical package was used for data analysis. RESULTS The positive rate of flu in ILI was 22.87%, and the difference between the positive rates of males and females was not significant (u=1.34, P=0.207). The detection rate in the elderly (≥60 years old) was significantly lower than that of the young and middle-aged people(P<0.05). In the confirmed cases, flu A, flu B and mixed flu accounted for 24.31%, 63.53% and 12.16%, respectively. The time distributions of flu A, flu B and the mixed were similar, all showing M-shaped bimodal curve. Flu B had the highest epidemic intensity with peaks about one week later than flu A, whereas the epidemic intensity of the mixed flu was the lowest with peaks after flu A and flu B. Males and females had similar ratio of the three types of flu, the difference of which was not significant (P=0.324). The ratio of different types of flu in patients of different ages was significantly different (P=0.021), and the ratio of flu A in the elderly increased remarkably at 29.83%. Among patients with flu, 80.77% were mild cases, 11.24% were complicated with bronchitis, and 7.99% were complicated with pneumonia. No significant difference was found in the incidence of lower respiratory tract infections among different types of flu and different genders. However, the incidence in the elderly was significantly higher than those of the young and middle-aged people (P<0.05). CONCLUSION The flu outbreak in this region during the winter and the spring presents some new features. It is necessary to take targeted measures to protect the elderly patients, update vaccination strategies and strengthen the public immunity barrier against flu.