The invention discloses a sulfur-containing polymer with high refraction index, a preparation method and an application thereof and belongs to the field of high-molecular optical materials. The sulfur-containing polymer has a structure as shown in a formula I or II. The sulfur-containing polymer, the preparation method and the application disclosed by the invention have the advantages that the sulfur-containing polymer is prepared by adopting sulfydryl-containing carboxylate ester monomers and allyl-containing triazine or silane compound monomers as materials and adopting a thermocuring method, the whole preparation process is simple, and the prepared sulfur-containing polymer is high in refraction index and good in mechanical property, and has higher application value in the aspects of optical lenses, LED (Light Emitting Diode) packaging materials and the like.