In order to study a simple and reasonable risk assessment method for safety factor of LNG storage tank, combined with event tree method and risk assessment theory comprehensive analysis method, the preliminary hazard analysis is carried out, and then the single model of LNG storage tank is analyzed upon the conclusions and the quantitative data of each risk event for LNG tank is calculated. Finally, this paper puts forward specific safety precautions for the safe operation of the LNG plant to effectively prevent or reduce the occurrence of the safety production accident. The research shows that the use of analytic hierarchy process is convenient and efficient, and it has guiding significance for single unit risk assessment.