The invention belongs to the technical field of electrochemistry, and particularly relates to an asymmetric diaphragm and an application thereof in a lithium-sulfur rechargeable battery. The asymmetric diaphragm comprises a polymer matrix layer and a conductive carbon layer, wherein the conductive carbon layer is adhered to the polymer matrix layer; and a main body of the conductive carbon layer is a carbon material, and is adhered through a binder or self-adhered through the carbon material. The conductive carbon layer contacts a composite sulfur anode when applied to the lithium-sulfur rechargeable battery; and the polymer matrix layer faces a cathode and contacts lithium metal. The asymmetric diaphragm is formed by the electrical conductivity and high specific surface area characteristics of the carbon material and the adhesive property of macromolecules; the utilization rate of a positive active material can be effectively improved under the condition of relatively low conductive layer additive amount; and polysulfide migration can be inhibited, so that the anode capacity and the cycling stability of the battery are improved.