Preparation method of crystal violet lactone

The invention discloses a preparation method of crystal violet lactone. The method comprises the following steps of: undergoing a condensation reaction to obtain a condensation reactant solution containing colorless crystal violet lactone, neutralizing the condensation reactant solution with a strong alkali solution, filtering, adding a transition metal catalyst into the filtrate, oxidizing and filtering to obtain crude crystal violet lactone; and dissolving the crude crystal violet lactone in an organic reagent, performing acid washing, alkali washing and water washing at the temperature of 70-80 DEG C, adding active carbon, dehydrating and performing filter pressing at the temperature of 100-120 DEG C, crystalizing, separating, washing the organic reagent away from a filter cake with a low-boiling-point hydrocarbon solvent, and drying to obtain the crystal violet lactone. The preparation method has the advantages of high total yield of crystal violet lactone, good product quality, low preparation cost, simp