Disclosed is method of fabricating sulfur-infiltrated mesoporous conductive nanocomposites for a cathode of a lithium-sulfur secondary battery, whereby a cathode material having a relatively high content of sulfur is fabricated and a high energy density in a lithium-sulfur secondary battery is realized, including: a) performing thermal treatment on sulfur particles in a reactor at a high temperature to melt the sulfur particles; b) adding a mesoporous conductive material in macroscale to a sulfur solution in the reactor; c) pressurizing the mesoporous conductive material in macroscale in the reactor so that the mesoporous conductive material in macroscale is completely immersed in the sulfur solution, and then maintaining the pressurized and molten state; d) cooling the sulfur particles and the mesoporous conductive material in macroscale so that sulfur within pores of the mesoporous conductive material in macroscale is crystallized; and e) grinding sulfur-infiltrated mesoporous conductive composites to fabricate sulfur-infiltrated mesoporous conductive nanocomposites.