The invention discloses a lithium-sulfur battery cathode material and a preparation method thereof. The cathode material is formed by in-situ compositing of a mesoporous metal-organic framework and elemental sulfur. The mesoporous metal-organic frame is of a laminated pore structure consisting of a macro pore, a meso pore and a micro pore, wherein the pores are communicated with one another. The structure can adsorb more elemental sulfur and can simultaneously inhibit the dissolution of sulfur elementary substance and multi-sulfur compounds in electrolyte, so that the cycle performance of a lithium-sulfur battery is improved and high utilization rate of an active substance of the cathode material is kept. A sulfur and metal-organic framework material composite cathode material is prepared by a two-step process of low-temperature liquid phase composition and sulfur extraction, a composite material precursor with homogeneously dispersed high load sulfur content can be obtained through in-situ compositing at a low temperature with a liquid-phase preparation method, redundant sulfur on the surface of the precursor and in pore passages is extracted by an organic solvent, the aperture of the composite material can be further effectively adjusted and controlled, selective distribution of sulfur is realized, and the composite material with excellent electrochemical performance is obtained. By adopting the preparation method, the distribution of the sulfur in the composite material can be effectively improved, and the electrochemical performance of the composite material is optimized. Meanwhile, the preparation method is simple and is easy to perform industrially, and mass production is facilitated.