Abstract: Since 2016, the outlet pipeline of the feed heater to fractionation column in fluidized catalytic cracking and delayed coking diesel hydrogenation unit started to vibrate. In order to alleviate vibration, the E-205 outlet pipeline was fixed to the steel beam of the fractionation frame, and vibration of the pipeline was alleviated. However, since May 2017, the vibration of the E-205 outlet pipeline was intensified, leading to vibration of the whole fractionation frame, and the frame vibration drove the reflux tank, the attached pipeline and the relief valve of the stripper vibrating. The reasons were analyzed: the unit blended straight-run diesel and produced the grade Ⅴ of the national standard diesel led to the increase of the light naphtha components generated by cracking in the hydrogenation reaction. The light naphtha components gradually accumulated within the stripper which caused the increase of the light components in the fractionation column feed, the rising of vaporization rate of medium within the E-205 outlet pipeline, and the increase of gas phase velocity, thus led to pipeline vibration. Through the implementation of the technological transformation, the recirculation oil of the stripper was changed to the hydrocracking unit stripper, the light components were transferred from the stripper, and the vibration was obviously alleviated.