Disclosed is a floating island construction method for overall transplantation of sandy soil plants, the method comprising the following steps: separation from a surrounding soil body; construction of a buoyancy tank device (13); and waterproof construction, so as to construct a plant floating island from plants to be transplanted in a reservoir area. The floating island protects all the root systems of the plants and most of the undisturbed soil, improves the survival rate, preserves the unique landscape of an original habitat, and can be constructed at the same time as water conservancy project construction, which saves on the construction period, saves costs, and is convenient for on-site overall scheduling.