The invention discloses a fresh water storage device and is mainly suitable for storage of fresh water at islands. The fresh water storage device comprises a floating body reservoir used for storing fresh water. The floating body reservoir comprises a plurality of spliced floating body units, and every two adjacent floating body units are connected together by a sealing connection assembly and are communicated. The fresh water storage device also comprises a fixing device used for fixing the floating body reservoir. The fixing device comprises a reservoir fixing net and a counter weight device used for holding the reservoir fixing net. By implementing the technical scheme, the floating body reservoir is mainly formed by assembling the plurality of floating body units of distributed structures, and the number of the floating body units can be increased or decreased according to the water demand. The fresh water storage device is simple in structure and convenient in assembling. The fresh water storage device also has the advantages of wind resistance, low cost and the like.