The occurrence of natural and human disasters can create heavy casualties in cities and urban areas and such a critical issue makes it inevitable to pay a great deal of attention to the vulnerability and safety aspects of cities and the accessibility to the urban welfare standards from the perspective of passive defense. The geostrategic location of Koohdasht city in Iran and its vulnerability against medium risk earthquakes as well as the strategic defensive role of the city in western parts of the country highlights the vital importance of vulnerability against earthquakes in Koohdasht city. This is a descriptive analytical research with a theoretical- applied essence. In order to achieve to the objectives of the survey, the critical and sensitive uses were identified based on the existing references and the spatial data bank was extracted using Delphi method and based on a survey consisted of 20 pundits. On the other hand, the principle of adjacency was taken into account. Based on the effectiveness of various indicators the combined model of FAHP-GIS was utilized to design the location model and the final raster of the vulnerability of urban infrastructures was provided using Arc GIS software and Spatial Analysis tools through the application of fuzzy overlay functions. The results of the study indicated that about 68 percent of the city infrastructures by meeting the conditions of adjacency between 0.29-0.55 and the vulnerability in the range of 0.45-0.71 fell in the high vulnerability zone.