The invention discloses a capacity-increasable aerial insulated cable, belongs to the technical field of an insulated cable and particularly relates to a capacity-increasable aerial insulated cable. The invention provides a capacity-increasable aerial insulated cable with high electrical conductivity and a good protecting effect. The capacity-increasable aerial insulated cable comprises an upper end polyethylene sheath and a lower end polyethylene sheath; the upper end polyethylene sheath is connected with the lower end polyethylene sheath by a vertical connecting rib; and the size and the sheath interior capacity of the upper end polyethylene sheath are greater than those of the lower end polyethylene sheath. The capacity-increasable aerial insulated cable has the structural key points that a duralumin molded wire stranded layer and a semiconductor layer are sequentially arranged inside the upper end polyethylene sheath from inside to outside; the duralumin molded wire stranded layer is formed by connecting a plurality of duralumin molded wires, of which the longitudinal sections are of an isosceles trapezoid shape, in a radial, seamless, tight and staggered manner; a waterproof layer is arranged inside the lower end polyethylene sheath; a plurality of loose tubes are arranged in the waterproof layer; and optical fibers are arranged in the loose tubes.