Preparation method of naphthol AS

The invention relates to a preparation method of naphthol AS. The method comprises a condensation process, an alkali cooking process, a filtration process, a drying process and a tail gas recycling process, wherein the condensation process comprises the following steps: 1) adding chlorobenzene and an organic solvent into a suspension pot; 2) after stirring and mixing, adding 2-hydroxy-3-naphthoic acid and an oil soluble ionic dispersant, stirring and adding aniline into the suspension pot; 3) filling materials in the suspension pot into a condensation reaction kettle and dropwise adding mixed liquid of phosphorus trichloride; 4) after the completion of dropwise adding of the mixed liquid of the phosphorus trichloride, heating with steam to obtain condensation materials. The preparation method of the naphthol AS provided by the invention has the benefits that a produced naphthol AS product has good quality and high yield; as the oil soluble ionic dispersant and the organic solvent are added in the condensation process, the dispersion of particles in suspension liquid is more uniform, and the coagulation phenomena cannot occur, so that the condensation process reaction is complete, the time of the condensation process is shortened, and the economic benefit is improved.