Influenza B virus (IBV) is a segmented negative-strand RNA virus, which often causes local outbreak or seasonal epidemic along with influenza A virus (IAV) in the world. It is pathogenic to children, teenagers and elderly people and has a higher mortality rate in children and adolescents, so it poses a serious threat to public health and health. IBV is more likely to cause complications than IAV and the disease burden of IBV even exceeds IAV in the epidemic season. Recently, especially after winter of 2017, IBV has become the dominant strain in many areas of our country and seriously affects people’s health. In view of this, this article reviews the structure, epidemiology, immunology and prevention of IBV, aiming at enhancing public’s perceptions of the virus and providing reference for making strategies for prevention and control of influenza B.