Abstract: 2-hydroxy-5-octyl phenyl ethyl ketoxime is prepared by three-step method using tetrachloroethylene as solvent, p-(tert-octyl) phenol, acetyl chloride, anhydrous aluminum chloride and hydroxylamine hydrochloride as raw materials. The effects of anhydrous aluminum chloride dosage, acetyl chloride dosage, Fries rearranging temperature, dosages of hydroxylamine hydrochloride and acid-binding agent anhydrous sodium carbonate in oximation reaction on the yield of 2-hydroxy-5-octyl phenyl ethyl ketoxime are investigated. The results show that the reaction rate of 2-hydroxy-5-octyl phenyl ethyl ketoxime production yield reaches 64.9 % under optimum reaction conditions: the mole ratio of anhydrous aluminum chloride, acetyl chloride and p-(tert-octyl) phenol is 1.5:2:1. Fries rearranging temperature is 120 ℃ and the mole ratio of anhydrous sodium carbonate, acetyl chloride and p-(tert-octyl) phenol is 0.5:1:1. The molecular structure of the product is characterized with nuclear magnetism resonance spectrum.