Abstract: The immersion process of a U-shaped pipeline involves problem of multi-body coupling, irregular structural shape, and coordination of suspension cables lowering, etc. To ensure construction safety and accuracy, based on the hydrodynamic analysis software OrcaFlex, a numerical analysis model for a U-shaped river-crossing pipeline in the immersion process was established. The dynamic tension of the suspension cables and mooring ropes, the dynamic response of the pipeline and its stress distributions along its length, and the dynamic response of the steel buoy were explored under typical case. The sensitivity of key parameters of the suspension cables tension was discussed. The results showed that the immersion process was safe and reliable in general, but improper operation could easily lead to excessive cable tension. In the actual construction, it was recommended to deflate the airbags at two ends of the pipeline firstly and deflate the airbags in the middle secondly, and the lowering speed of the suspension cables should be coordinated with the deflate time of the airbags, the lowering speed or initial lowering time of the middle suspension cables should be slightly later than that of the two sides suspension cables. It is necessary to real-time monitor the tension of the suspension cables and the dynamic response of the pipeline. This study can provide valuable references for the actual construction and other similar projects.