Abstract: Influenza B virus is one of the pathogens causing seasonal influenza, which circulates in population every year at different levels. Influenza B virus differs with influenza A virus in terms of gene structure, encoding protein and so on. Influenza B virus mainly causes local outbreaks or epidemics, and tends to infect specific population; Complications would occur when infected with influenza B virus in addition to the typical symptoms of the infection. In some epidemic season, influenza B virus would cause more heavy disease burden than influenza A virus. It is necessary to strengthen the surveillance for influenza B virus and related research to provide scientific evidence for the recommendation of influenza vaccine and development of novel antiviral drugs.