Numerous accidents have happened in all types of moored units, permanent and mobile. The problems related to mooring system failures are collision, abrasion, anchors etc. These problems have impact on people, environment, assets and reputation of the company. The objective of this paper are to determine the frequency of failure, to categorize severity of failure of mooring system and to rank the particular hazards by dividing the dimensions of frequency and severity into risk matrix. This work proposes HAZOP (Hazard and Operability) analysis to evaluate risks related to accidents in mobile mooring system. In qualitative assessment the accident risk level and acceptance criteria were established through a scoring system. The result of this methodology can be used to prevent future damage and aid to set a priority of maintenance based on hazards ranking.