Thought of High Frontiers is still the foundation of theory of U.S. strategy of outer space in the 21^st Century. The thought holds that the outer space is the New Frontier of the human beings，and if the United States wants to maintain its leadership in the world，it must keep its superiority in the outer space. With the development of the capability of the outer space of the United States，the military operation，governmental activities，business and trade，social lives of the U.S. have been more and more depending on its properties in the outer space. That has lead to the results that the dual character of both importance and fragility of the properties of the U.S. in the outer space has been more sticking out. The “National Space Policy of the United States of America” issued by Obama Administration in June 2010 has changed the outer space strategy of Bush Administration with the characteristics of unilateralism，and has stressed the international cooperation in the outer space with other countries. However，its major purpose is still to maintain the leadership of the U.S. in the outer space and the superiority of the development of technology of the outer space of the U.S.