The invention discloses a large-scale algae cultivation device, and belongs to the technical field of marine algae cultivation. The large-scale algae cultivation device adopts the structure that cultivation ropes are distributed in a floating ring in a spider web manner, and each mesh serves as a cultivation unit; a plurality of metal ring buckles are uniformly distributed on the floating ring; three lugs are arranged on each metal ring buckle, and used for connecting the corresponding cultivation rope, an upper part bearing rope and a lower part bearing rope; a solar panel is attached to the upper surface of a float bowl and used for supplying power for the device system. Interrupted times are set in a single-chip microcomputer to control regular rotation of a motor, so that the cultivation floating ring can adjust the cultivation depth according to growth characteristics of algae; in addition, an anchor of the device can generate manual upstream underwater, so that more nutrients are provided for the growth of the algae, and the anchor plays the role of artificial fish reefs.