The invention belongs to the field of organic synthesis and specifically relates to a preparation method of sodium p-styrenesulfonate. The preparation method comprises the following steps: (1) (2-chloroethyl)benzene and SO3 react to generate p-sulfonic acid-(2-chloroethyl)benzene; and (2) the p-sulfonic acid-(2-chloroethyl)benzene prepared in the step (1) reacts with NaOH to generate sodium p-styrenesulfonate. The invention has the following advantages: (2-chloroethyl)benzene adopted in the invention is cheap and easily available and its unit consumption and cost are lower. In addition, motherliquor produced by the method can be subjected to centrifugal separation to obtain pure sodium p-styrenesulfonate. Part of sodium p-styrenesulfonate dissolved in the primary mother liquor can be recovered to obtain a recycled product. Recovered secondary mother liquor almost contains no sodium p-styrenesulfonate, and concentrated secondary mother liquor can recover industrial sodium chloride. Thereby, the pollution of ''three wastes (waste gas, waste water and industrial residue)'' to the environment is reduced. In addition, the sodium p-styrenesulfonate prepared by the method is not easy topolymerize. The prepared product is not easy to polymerize when being placed or dissolved for use, and the property is stable.