Abstract: Influenza (simply as the flu), a kind of acute respiratory infection, is a commonly-seen contagious disease in human, wild birds, swine, horse and other fowl. Its onset is soon, infects quickly and spreading wide. It is a great danger to people's lives. There have been epidemic records of influenza in each century since the 6th century, among which the 1918's caused the most severe consequence. This article contains three aspects. They are naming and classification of flu, epidemic history of flu, Avian Influenza and Swine Influenza. The progress in diagnosis, treatment and prevention on flu are also reviewed. The main purpose of this research is to profoundly reconsider the relationship between human and nature, human and animal as well as human and environment. We need to work hard to reach an ideal harmonious state.