The invention discloses an installation method for an energy-saving fin keel of a ship. The installation method comprises following steps: actually measuring the contour line of an outer plate of a stern tube shaft in an installation region of an energy-saving fin, utilizing the actually measured line shape and an installation angle of the fin keel to find a primary installation position line of the fin keel on the stern contour of a tube shaft, utilizing the line shape to cut off the remaining amount of the fin keel in advance, compiling control program of deviation of the fin plate, correlating three-dimensional coordinates of a fin keel point measured by a total-station instrument to the positioning deviation of the fin keel for real-time tracking and positional guiding of the fin keel, reinforcing the fin keel prior to welding and formulating reasonable program of welding process, utilizing positioning deviation of the fin plate to control program so that welding influence upon installation of the fin keel is adjusted within the controllable range. The installation method for the energy-saving fin keel of the ship is capable of shortening time spent on positioning and installing the energy-saving fin keel in the dock phase and effectively reducing period of newly constructing a dock of the ship and dock-repair period of repairing the ship so that construction or cost of the ship or dock repair can be effectively saved.