Method for purifying herbicide intermediate

The invention discloses a method for purifying 1-(2,4-dichlorophenyl-5-amino)-4-difluoromethyl-4,5-dihydro-3-methcyl-1H-1,2,4-triazole-5-ketone and similar compounds. The method comprises the steps that after a coarse product is dissolved by selecting mixed solvent of alcohols and water, the PH value of the material is regulated with a hydrochloric acid solution with the concentration of 30%, after impurities are dissolved and the product is salified, filtering is performed to remove the impurities dissolved in filtrate, and a high-purity product is acquired in a hydrochloride solid form after being cooled; the hydrochloride product is dissolved in water, an alkaline solution is dropwise added for neutralization, and the high-purity product is separated out. According to the method, the defect that in the prior art, impurity removal is not thorough due to the fact that a by-product is poor in solubility when elution is performed by adopting dichloromethane and acetone solvent is overcome, and the purity the p