Par-ester is an important intermediate of reactive dyes, which is used to synthesize EF type, KN type, M/KM type, ME type and other ethylene sulfone-containing reactive dyes. Dye intermediates for the manufacture of vinyl sulfone type reactive dyes. Par-esters are temporary water-soluble groups that not only improve the solubility of dye application, but also have low affinity for fibers of reactive dyes containing hydroxyethyl sulfone sulfate groups when dyeing.