Objective:To evaluate the immunogenicity of a quadrivalent influenza virus subunit vaccine in a healthy population aged 3-64 years.Methods:Healthy people aged 3-64 years old were selected as the study subjects, and a randomized, blind, positive controlled, non-inferiority test was adopted. The subjects were randomly inoculated with one dose of the corresponding experimental vaccine or control vaccine in a ratio of 1∶1. Blood samples were collected from all subjects before and at 28 d after immunization, and hemagglutination inhibition (HI) test was used to measure the levels of antibodies against H1N1, H3N2, B/Victoria (BV) and B/Yamagata (BY) in serum. The geometric mean titers (GMT), geometric mean increase (GMI), positive conversion rates and protection rates of antibodies against the four types of viruses were analyzed.Results:A total of 2 157 subjects aged 3-64 years were included, including 1 074 in the experimental group and 1 083 in the control group. There were no significant differences in the GMT or protection rates of antibodies against H1N1, H3N2, BV or BY before immunization between the two groups ( P>0.05), and the two groups were balanced at baseline. After full immunization, the GMI of antibodies to H1N1, H3N2, BV and BY in the experimental group was 11.16, 17.77, 9.61 and 15.13, respectively; the positive conversion rates were 84.08% (903/1 074), 92.46% (993/1 074), 86.03% (924/1 074) and 91.71% (985/1 074), respectively; the protection rates were 96.74% (1 039/1 074), 97.58% (1 048/1 074), 88.08% (946/1 074) and 94.97% (1 020/1 074), respectively. In the experimental group, the GMT of each antibody increased by more than 2.5 times after immunization; the lower limit of the 95%CI of the positive conversion rate was higher than 40%, and the lower limit of the 95%CI of the protection rate was higher than 70%. The lower limit of the 95%CI of the difference in the positive conversion rate of each antibody between the experimental group and the control group was >-10%, and the lower limit of the 95%CI for GMT (experimental group)/GMT (control group) was over 2/3. Conclusions:The experimental vaccine had good immunogenicity and was non-inferior to the control vaccine in the population aged 3-64 years.