The present invention relates to a polymer-sulfur copolymer, a preparation method thereof, and a lithium-sulfur battery including the same.In the case of the polymer-sulfur copolymer according to the present invention, since the carrier is polymerized, there is no possibility that the carrier is eluted, and since the sulfur is covalently bonded to the polymer and uniformly distributed in a certain size in the copolymer, when used as a positive electrode active material for the lithium-sulfur battery, the problem of elution of the polysulfide can be improved. In addition, the polymer-sulfur copolymer according to the present invention has a high sulfur impregnation amount, thereby making it possible to realize a high capacity battery.