The invention discloses a preparation method of a high-energy density lithium-sulfur battery positive electrode material, and belongs to the technical field of the preparation of lithium-sulfur battery positive electrode materials. The preparation method comprises the following steps: reacting hydrochloric acid with sodium thiosulfate to prepare nanometer sulfur, coating the nanometer sulfur with silica to prepare microspheres, loading the prepared microspheres to a polyurethane foam material, plating copper to prepare a foam copper material, melting internal nanometer sulfur single substance in the calcining process of the foam copper and sublimation sulfur to fill internal foam copper pores, and calcining the filled foam copper material and external sublimation sulfur to generate penetration. The high-energy density lithium-sulfur battery positive electrode material has the advantages of effectively enhanced elemental sulfur load, improvement of the energy density of lithium-sulfur batteries, ,excellent stability, excellent cycle life, rapid activation in the cycle process, and effective improvement of the cycle and rate performances of the batteries.