The present invention relates to a method for preparing a β-lactam derivative, wherein a substituted N-quinoline-3-butenamide derivative is used as a substrate to react with a toluene derivative or a heterocyclic derivative at 90-150° C. in the presence of DTBP and a copper salt catalyst, to prepare a β-lactam derivative. According to the method of the present invention, a variety of β-lactam derivatives can be obtained with a high yield. The reaction of the present invention has mild reaction conditions, and simple reaction operation and post-treatment process, and is suitable for large-scale production.