Taking liquid ammonia transport tanker as the research object,the influencing factors of the liquid phase flange sealing performance of the tank car were analyzed.It is pointed out that the gasket failure deformation,the change of the internal pressure load of the medium and the change of the ambient temperature are the main factors affecting the flange sealing system.The finite element model of liquid phase flange was established to analyze the influence of failure deformation of gasket,internal pressure load and ambient temperature on the sealing performance of bolted flange joint under preload condition.The simulation result shows that there is a depressed area between the inner core plane of the valve root of the liquid phase flange emergency shut-off valve and the flange sealing gasket,which reduces the sealing area of the gasket by 20.9% and reduces the sealing performance of the flange joint.The fluctuation of the internal pressure load of the medium has little effect on the sealing performance of the system.The temperature change has a great influence on the residual pressure stress value.The minimum pressure value that determines the sealing condition decreases with the temperature drop,thus affecting the sealing performance of the flange.