The invention provides a method for measuring the highest binding rate of As atoms in GaAs molecular beam epitaxy growth process. The method is characterized by comprising the following steps: enabling a Ga-rich surface and an As-rich surface to alternately appear in the GaAs growth process by utilizing the change of a Ga atom beam; recording the time of reconstruction changes of the surfaces; and finally obtaining the highest binding rate of the As atoms in the growth process through an expression for solving the total quantity of the surplus atoms on the surfaces. The method is characterized in that the Ga-rich surface and the As-rich surface alternately appear through a switch but not limited to a second Ga source shutter, ah RHEED method is used for measurement, and the final result does not involve the actual total quantity of the atoms, so that the highest binding rate of the atoms is related to the Ga and As beam values directly measured by a beam gauge. The method provided by the invention is significant to the utilization of MBE preparation materials and particularly the mobility enhancement epitaxy growth (MEE) mode.