This paper presents a tank farm safety assessment method based on the structure entropy weight method and cloud model. This method considers the natural fuzziness of safety and fluctuation in the safety level, which can not only provide the assessment index weights combined subjectively and objectively but also consider the fuzziness of the safety level boundary. Finally, this method can be used to obtain a scientific safety level to prevent accidents. In addition, taking the tank farms of four petroleum and petrochemical companies as examples, this safety assessment method is verified to be an effective tool for safety management.