The invention discloses a lithium-sulfur battery diaphragm. The lithium-sulfur battery diaphragm comprises a conductive layer composed of a conductive carbon material, flaky tungsten disulfide and a first binder, and an insulating layer composed of a second binder, wherein the insulating layer is arranged on one side of the conductive layer; the conductive layer is used for limiting a shuttle effect of polysulfide and providing sufficient spaces and sites for nucleation and growth of sulfur; and the insulating layer is used for blocking direct contact short circuit between an anode and a cathode, improving the mechanical strength of the diaphragm, and being beneficial to large-scale production and application of the diaphragm. The invention also discloses a preparation method of the lithium-sulfur battery diaphragm, which comprises the following steps: preliminarily dissolving the first binder and the second binder in acetone, and then melting the first binder and the second binder into long-chain structures by adding N-methylpyrrolidone or heating, thereby reducing the crystallinity of the diaphragm and improving the mechanical properties of the diaphragm.