Abstract: Based on a brief review of the development history of atomic absorption spectroscopy technology, this paper summarizes the structure of the atomic absorption spectroscopy system used for in-situ real-time monitoring of the flux in molecular beam epitaxy, and reviews the selection and parameters of key components required to build the system. Meanwhile, it also summarizes the background reference method of atomic absorption spectroscopy, error sources and the drift correction methods. The advantages of atomic absorption spectroscopy technology in real-time on-line and multi-element monitoring in molecular beam epitaxy systems are analyzed. The developing process of the application is also reviewed. On this basis, an improved scheme of atomic absorption spectroscopy technology in molecular beam epitaxy is proposed, and the new application scenarios of this technology are discussed.