Abstract: Mamdani fuzzy inference system was used to study the tank vehicle's safety state for hazardous chemicals road transportation in this paper.In order to meet the real-time requirement of the safety assessment model,the evaluation index system was established based on the variables monitored by the tank vehicle condition monitor system.And then an evaluation set containing five safety states was set up,and the membership function and inference rules were built.Finally,this model was used to study the safety state of LNG tank during gas leakage.This model can evaluate the safety state of tank vehicle,provide guidance for drivers' decision making,and have potential application in practice.