Quantitative risk assessment and reliability are essential issues in modern safety to make reliable decision. Risk assessment approaches are designed primarily to reduce the existing risk inherent in engineering system to a level considered tolerable and maintain it over time. This reduction is often achieved by successive interposition of several protective barriers between the source of danger, which can be an industrial process, and potential targets are people, property and the environment. Layer of protection analysis is an approach to estimate the risk by quantifying risk results. A fuzzy set is a new mathematical tool to model inaccuracy and uncertainty of data based on the surgeon method. In this study, new model proposed to deal with quantitative risk assessment and precise the severity of the scenario and determine the safety integrity level SIL based on LOPA and Bow-tie using fuzzy set, and the results illustrates that this models is more powerful than logical and arithmetic computation.