Abstract: The Fukushima nuclear accident has had a far-reaching impact on nuclear energy and nuclear safety. Since then, major nuclear power countries and organizations have carried out experience feedback and revision of laws and regulations. From the Recommendations for Enhancing Reactor Safety in the 21st Century issued by the United States in July 2011 to the MBDBE regulation（10CFR § 50.155） issued in September 2019, the U.S. Nuclear Regulatory Commission（NRC） and the nuclear industry have carried out a series of studies in eight years, issued relevant orders and prepared regulatory guidelines（RG） and corresponding technical documents of Nuclear Energy Research Institute（NEI） to meet the requirements of relevant regulations and regulatory guidelines. Based on the investigation of the response actions and specific processes of the United States after the Fukushima nuclear accident, this paper interprets the technical contents of MBDBE regulations, and summarizes the supporting guidelines and NEI technical documents in details. Based on the above work, this paper summarizes some key problems that can be used for reference for related domestic work, and puts forward some suggestions.