To perfect the emergency management system of our country is an important starting point to promote the modernization of our country’s governance system and governance ability. Based on the concept of top-level design, this paper uses the research method of policy literature measurement to deeply explore the important policy texts related to the work report and emergency management of the central government, and analyzes the process and mechanism of top-level design changes of China’s emergency management system since the founding of the people’s Republic of China. The research shows that since the founding, the emergency management system in China has gone through the periods of disaster relief, comprehensive disaster reduction, emergency management and public security; the top-level design of the emergency management system has also changed significantly in different periods, among which the change of the top-level design decision layer promotes the central government’s attention to the emergency management work, the change of the related layer promotes the normalization of the emergency management function, while the operation layer, changes of national central task, national governance mode, economic development level and social emergency demand are the important driving forces of the changes of top-level design of emergency management system in China. In the future, the central government should pay attention to these elements in the construction of emergency management system.