The invention discloses a method for preparing a quinazolinone derivative. According to the invention, a 1-pyridyl indole compound is taken as an initiator and is reacted in air to prepare a product,the raw materials are easily available, and the types are wide; the product obtained by the method has the advantages of various types and wide application, and can be used for synthesizing drugs; inaddition, the method has the advantages of simple process, mild reaction condition, high yield of target product, little pollution, and simple reaction operation and post-processing process, and is suitable for industrial production.