Abstract: The magnitude of an earthquake is closely related to seismic disasters and directly impacts the safety of people's lives and property. The mandatory national standard GB 17740—2017 "General ruler for Earthquake Magnitude" was formulated in accordance with the requirements of the seismic emergency management system established under the " Law of the People's Republic of China on Protecting Against and Mitigating Earthquake Disasters ". This standard is applicable to earthquake monitoring, earthquake emergency response, information dissemination, scientific popularization, news reporting and other work related to earthquake magnitude. In this paper, The purpose of preparation, legal basis, and overall technical design points of the mandatory national standard GB 17740-2017 general ruler for earthquake magnitude, as well as the social and professional application requirements of earthquake magnitude, the scope of application of different earthquake magnitudes, and the docking relationship were introduced. Magnitude is a fundamental parameter of earthquakes, with a wide range of applications. Different application fields may have varying understandings of magnitude. Mastering these technical points in this paper is of great significance for scientifically and accurately determining earthquake magnitude and correctly using earthquake magnitude.