The city is a dense human habitat that requires security and security in all physical, social, economic, cultural and other aspects due to human presence. The purpose of this study was to investigate the vulnerability of the degraded texture of the Port of Mahshahr from the standpoint of passive defense using hierarchical fuzzy method. The present paper is applied in terms of purpose and in terms of descriptive-analytical method. Accordingly, Delphi method was used to identify vulnerable elements of the city against military invasions and hazards. The experts of this study were 20 experts of urban affairs from the personnel of 7 important organizations in this field (governor's office, municipality, Red Crescent, law enforcement, Basij and IRGC, and according to experts' opinion, finally 6 indicators and 15 Criteria were selected to measure the vulnerability of the study area. In the next step, data layers and indices were prepared in Arc / Map 10.2 environment and finally, using the fuzzy hierarchy method, the vulnerability zoning map was prepared in three high, medium, and low risk zones. The widespread Mahshahr Port is observed to have high vulnerability distribution in all areas, accounting for about 27.2% of the total area. Eighty-five percent of the areas with moderate vulnerability and the rest of the area with low vulnerability were allocated to these areas with more open spaces but more open spaces and new buildings.