During the process operation and accident discharge of an ethylene plant, it was found that the back pressure of flare was abnormally increased during equipment emptying and purging as well as acetylene hydrogenation reactor switching and discharging to cold dry flare. During the major overhaul in 2024, endoscopes and tube robots were used to check the inner tube in jacket of the cold dry flare, and the inner tube was found to be severely deformed. The causes of inner tube deformation were analyzed by calculating the parameters of the cold dry flare including daily operation, harsh working conditions and piping design, and targeted solutions were developed to ensure the safe emission of the flare system.