The invention discloses a method for detecting dairy products by using a matrix assisted laser desorption ionization mass spectrometry. According to the invention, on one hand, a few biological sample is rapidly and efficiently used in the mass spectrometry to realize qualitative and quantitative determination of to-be-measured molecules, and the strong background noise interference brought by a traditional matrix can be removed, ionization can be effectively performed on the molecules in a target system, and the better detection effect can be achieved. The above method can realize specific detection of assigned type molecules, eliminates other molecules interference and has certain salt resistance performance, and is suitable for detection of a biological liquid system. The method can be taken as a rapid and efficient detection means, brings little sample consumption, in favor of miniaturization of a biological sample database, and is worth of popularization and application.