The invention discloses an installation method for a full-rotation steering oar. The method includes the following steps that firstly, before installation, a split type full-rotation steering oar is produced, wherein the split type full-rotation steering oar comprises an upper half full-rotation steering oar section and a lower half full-rotation steering oar section; and secondly, in the installation stage, the upper half full-rotation steering oar section is lifted to a hull base to be fastened from the interior of an auxiliary hole above a stern deck, and the lower half full-rotation steering oar section is jacked from the bottom of a stern to be connected with and fastened to the upper half full-rotation steering oar section. The method solves the problems that the requirement for the equipment arrival receiving period is high, the operation safety coefficient is low, and the installation manufacturability is poor.