The invention relates to a lithium-sulfur battery high-molecular composite cathode material and a preparation method. The material is prepared from the following components in percentages by weight: 60% to 85% of elemental sulfur and 15% to 40% of poly (3,4-ethylene dithio-thiofuran); the poly (3,4-ethylene dithio-thiofuran) is taken as a main fiber-forming polymer, and the elemental sulfur is uniformly dispersed in a spinning solution of the poly (3,4-ethylene dithio-thiofuran) so as to realize molecular dispersion by using the characteristic that the elemental sulfur is dissoluble in organic solvents such as carbon disulfide and carbon tetrachloride; and then nanofiber is prepared by using an electrospinning technique. In the nanofiber, the elemental sulfur as a cathode active material is uniformly distributed in the fiber, the poly (3,4-ethylene dithio-thiofuran) as carrier-clad sulfur can inhibit the dissolution of a polysulfide generated in an electrochemical process, and meanwhile an electron conveying passage is provided, so that the cycle performance of a lithium-sulfur battery can be obviously improved. The material is low in equipment requirement and simple in preparation technology, and is beneficial for industrial production.