Objective Small and micro reactors (hereinafter referred to as "SMRs") are characterized by their inherent strong safety, compact size, lightweight, and the capability to operate without refueling for several years. They play an irreplaceable role in both civil and defense sectors and have become a research hotspot in the international nuclear energy industry for nearly two decades. The United States has continuously advanced the research and deployment of SMRs, with its technological sophistication and research progress leading the international pack. The paper aims to analyze the promoting practices and development of the United States SMRs, providing the inspiration for the development of SMRs in China.

Method Through literature research and expert consultation methods, the application scenarios of SMRs were outlined, the primary approaches adopted by the United States to support the development of SMRs were analyzed, and the the latest progress of SMR technologies in the United States were summarized.

Result The application scenarios of SMRs mainly include power supply for remote areas, seawater desalination, heat and steam supply, marine propulsion, and space exploration. The United States mainly provides solid legal protection for the development of SMRs through legislation. The Department of Energy (DoE) provides comprehensive support for the commercialization of civil SMRs through a series of measures such as the GAIN program. The Department of Defense (DoD) supports the research and development of micro-reactors through the "Project Pele". The latest progress of various SMR technologies in the United States mainly includes NuScale, eVinci, Aurora, Pele, BANR, and Xe-100. Moreover, the prototype of the Pele reactor has commenced construction in September 2024 and is poised to become the first fourth-generation reactor to be commissioned in the United States.

Conclusion The development of SMRs in the United States has the following implications for China: firstly, adhere to state leadership and accelerate the development of SMR technologies through top-level design; secondly, achieve cooperation between enterprises and high-level research institutions to establish an advanced industry-academia-research scientific and technological innovation system; and thirdly, actively address user needs and strengthen international cooperation.