The Evolution and Practice of U.S. National Cybersecurity Strategy(Shen Yi) IT Revolution, represented by the vivid development of Internet in the world, has produced a global cyberspace since the late 1970s. As the initiator of Internet, while occupying an overwhelming advantage in the development of the ITrelated technologies, hardware, and software, the United States has already made a complete and comprehensive national cybersecurity strategy. The core goals of the strategy evolve from protection of the key infrastructure, to surveillance of the information flow in the cyberspace, to active defense including cross border action to mitigate the potential threats, and finally to the shaping of the context of global cyberspace. Since the end of the Cold War, especially since the beginning of the Obama Administration, with the United States suffering from a relative decline of power in the real world, the US has paid special attention toward the cybersecurity issues. Since the U.S. now still enjoys asymmetric advantages in the cyberspace, technological innovations and cybersecurity play more important part to ensure American national security. In the foreseeable future, the cybersecurity issue will gain a more important position within the framework of US national security strategy.