The present invention discloses a light metal matrix composite material cable core, which is characterized in that the cable core consists of a magnesium alloy matrix and continuous carbon fibre. The continuous carbon fibre has strength between 5000 and 5500 Mpa and uses polyacrylonitrile as raw material. The carbon fibre is evenly and parallelly distributed in the magnesium matrix. The carbon fibre takes 10 to 70 percent of the volume of the cable core. The mass percent of the composition elements of the magnesium matrix is as follows: Al of more than 5 percent and less than or equal to 9 percent, Zn of more than 0.5 percent and less than or equal to 2.5 percent, Pr of more than 0.1 percent and less than or equal to 1 percent, Zr of more than 0.3 percent and less than or equal to 0.9 percent, Nd of more than 0.03 percent and less than or equal to 0.09 percent, Y of more than or equal to 0.03 percent and less than or equal to 0.06 percent and the rest is magnesium. The manufacture method of the magnesium granules polymer composite material has simple art, no environment pollution and low production cost. The magnesium alloy composite material wire made by the method has sufficiently high mechanical properties, can be used as a cable core for reinforcing conductive bare aluminum twisted wire.