Abstract: The Safety Framework for Nuclear Power Source Applications in Outer space was jointly published by the Scientific and Technical Subcommittee of UN COPUOS and the International Atomic Energy Agency in 2007. The framework is focusing on the new areas of nuclear power sources (NPS), and its purpose is to provide technical guidance to promote the safety of NPS applications in outer space. Keeping consistent with the security framework, the United States gradually formed its national NPS safety mechanism which includes the National Environmental Policy Act, Presidential Nuclear Safety Launch Approval Process, NASA Procedural Requirements and National Response Framework. The United States has a relatively mature technical and legal system which was related to nuclear power sources security applications in outer space, especially in the aspects of assessment, approval process, allocation of responsibilities and the emergency reaction policies. In the coming building up of the outer space nuclear safety mechanism in China, the following ways can help China to make a similar U.S. National NPS safety framework, including special legislation, the establishment of a national nuclear safety assessment system, improving the government nuclear security management capacity and leading an international nuclear power sources forums.