The liquid-phase Beckman rearrangement of cyclohexanone oxime to ε-caprolactam with TsCl(p-toluenesulfonyl chloride) as catalyst and acetonitrile as solvent has been studied. The effects of catalyst, reaction temperature, reaction time, the dosage of catalyst, the amount of catalyst on the yield of ε-caprolactam were investigated. Under the optimized reaction conditions, cyclohexanone oxime 2.0g, TsCl 1.5g, solvent acetonitrile 20mL, reaction temperature 60℃, reaction time 2.5h, The conversion of oxime and the selectivity to ε-caprolactam were 98.4% and 93.6%, respectively. This method has an advantage of mild reaction conditions and Solvent acetonitrile can be reused.