Abstract: With respect to the multiple levels and complexity of safety assessment system for LNG liquefaction plant, comprehensive expansion assessment method based on entropy weight theory is used for safety assessment of the LNG liquefaction plant. In accordance with existing industry standards and codes for the LNG liquefaction plant and taking the equipment, environmental and human factors into account, a safety assessment indicator system for the LNG liquefaction plant is established and a matter-element model for the comprehensive safety assessment of matter-element is built to achieve quantitative calculation of entropy coefficient and comprehensive correlative degree so as to carry out comprehensive safety assessment for the LNG liquefaction plant. Case calculation results provide a safety level to the LNG liquefaction plant, and it indicates that the extension theory-based comprehensive safety assessment for the LNG liquefaction plant is valid.