The invention discloses a sulfur-containing optical resin monomer, a sulfur-containing optical resin and a preparation method thereof. The preparation method for the sulfur-containing optical resin monomer comprises the following steps: acquiring 1,1'-sulfo-bi (2-naphthol) by performing double displacement reaction on 2-naphthol p-sulfur dichloride, and then triggering reaction between 1,1'-sulfo-bi (2-naphthol) and epoxy chloropropane under the catalytic effect of tetra-n-butylammonium bromide, thereby acquiring the sulfur-containing optical resin monomer. According to the invention, the refractive index of the compound is increased by introducing a sulfur-containing electron-rich conjugate constitutional unit with high mole refrangibility into the sulfur-containing optical resin monomer, and a sulfur-containing optical resin substrate with high index of refraction and high purity is finally prepared through the curing reaction between the sulfur-containing optical resin monomer and1,4-xylyl-mercaptan.