In view of the high temperature of the reactor pipeline, the large wall thickness, the complex working conditions, and the severe stress allowed by the equipment nozzle.Two kinds of typical reactors in styrene plant were selected, and the flexible analysis and design of their inlet and outlet pipelines and high temperature nitrogen purge pipelines were carried out. By optimizing the pipeline scheme and selecting the appropriate spring support, the force of the nozzle could meet the requirements of allowable force. The selection of spring support under multiple working conditions was analyzed and compared, and the optimal scheme of pipeline design was selected by combining multiple factors.