Through risk assessment, very valuable data was provided for decision making about risk reduction, improvement of the surrounding environment of hazardous installations, planning for emergency conditions, acceptable risk level, inspection and maintenance policies in industrial installations, and other cases. The gas and petrochemical industries have always been considered by the safety and environment experts and professionals, because of their numerous and widespread hazards. The purpose of this research was to assess the risk ratio of the phases of 17 and 18 refineries of Asaluyeh. The research method used in this research was descriptive-analytical, and multi-criteria models (hierarchy analysis) and FMEA risk assessment model were used. The results of this research indicated that the risk of oil and gas installations infrastructure in the phases of 17 and 18 refinery, for a hard and special threat meant that the occurrence probability of air and missile attacks and cyber attacks and bombing in such installations were located at the primary degree of threats.