The denseness of urban public buildings and the complication of the underground space spur the enhancement of disaster prevention and mitigation planning. As a result, for the urban public buildings around the densely populated area, the establishment of public buildings disaster prevention system in urban and the study on some related questions lay the basis of disaster prevention and mitigation. Since the concept of public building have the different definitions in the national standards and different types of buildings require different signs on disaster prevention, the category of public buildings has been redefined according to international normative standards. Furthermore, the research on the types, colors, sizes and position of disaster prevention signs has been done according to the internal, external of building and evacuation routes aspects. Finally, the basic functions of disaster prevention sign system in and around the buildings and the settings of the disaster prevention sign system of different types of public buildings are proposed.