Throughout history，the production and interaction of information have been extremely important.However，information has been influenced by the process of human development through media dissemination.More than sixty years ago，Marshall McLuhan acutely captured the significance of media for mankind：media are an extension of mankind.This article rethinks this classic work by McLuhan and discusses how the development of media based on the extensions of man affected the development of human society.This article holds that McLuhan's works have a new significance in the age of the Internet：on the one hand，as the extensions of man，the media are a powerful weapon for society to oppose state intervention at the macro level，which means that the media are the“metronome”of the boundary between state and society；on the other hand，“the media are the extensions of man”means paying attention to the course of personal life and highlighting the background of life at the micro level.