The invention relates to a method for preparation of a naphthalene dispersing agent by using a naphthalenesulfonate recycled waste liquid; the method comprises the steps: taking a reextraction liquid obtained through complex extraction or a resin elution liquid obtained through resin adsorption separation or other concentrated pollutant waste liquids containing naphthalenesulfonate waste water, carrying out evaporation concentration or adding a sulfonation material synthesized from industrial naphthalene, adjusting to be a waste water concentrate with the solid content of 45%-60%, then adding concentrated sulfuric acid, adjusting the total acidity to 25%-30%, adding formaldehyde, carrying out a condensation reaction, after the reaction, adding an alkali, neutralizing, cooling and separating to obtain sulfate crystals, and thus obtaining the naphthalene liquid dispersing agent product. The dispersing agent prepared by the method can be widely applied in dyes, water coal slurry, pesticides, concrete and other industries. The invention provides the new method for comprehensive utilization of the naphthalenesulfonate waste liquid; the synthesized naphthalene dispersion agent relatively directly adopts industrial naphthalene as a raw material, so that the product cost is low; and at the same time, the naphthalenesulfonate waste water is effectively subjected to comprehensive governance, the environment is protected, and good economic benefits and environmental benefits are achieved.