The invention discloses a lithium-sulfur battery based on a sulfur-nitrogen self-doping positive electrode active material. According to the lithium-sulfur battery, the negative electrode is a metal lithium sheet; the electrolytic solution is a lithium bis(trifluoromethanesulphonyl)imide solution; the solvent is the mixed solvent of 1,3-dioxolane and ethylene glycol dimethyl ether according to a volume ratio of 1:1; LiNO3 is an additive; and the positive electrode is a positive electrode active material based on sulfur-nitrogen self-doping, wherein a 4-methyl-5-vinylthiazole-sulfur copolymer,electric-condition carbon black and hydroxymethyl cellulose sodium are uniformly stirred to obtain a mixed slurry, an aluminum foil is uniformly coated with the mixed slurry, and vacuum drying is performed to obtain the positive electrode, wherein the 4-methyl-5-vinylthiazole-sulfur copolymer is formed by carrying out melt co-polymerization on elemental sulfur and 4-methyl-5-vinylthiazole. According to the present invention, the high-sulfur-content copolymer can be prepared through the reaction of elemental sulfur and 4-methyl-5-vinylthiazole, and can be used as the positive electrode materialof the lithium-sulfur battery so as to greatly increases the active material content in the positive electrode.