Aiming at the risk brought by the anchor dropping of floating crane vessel to the subsea cable around the platform and reduction of the installation cost of the cable casing during the process of subsea cable casing post-installation, 3 kinds of methods are comparatively analyzed, which are anchor mooring crane, dynamic positioning vessel and on-platform installation, and the results show that the on-platform installation method is of great advantages in the installation period, cost and safety. The design and theoretical analysis are carried out for the on-platform installation technology of the cable casing, and the installation process is verified by the actual case. The results show that the new process can not only reduce the high risk induced by the hoisting operation of the floating crane vessel, but also significantly reduce the operation cost, and installing one cable casing can save 3 d of shipping time. The new technology can provide important reference for the subsea cable casing post-installation of the platform in service, and is expected to be promoted in the future.