Abstract: Hysteresis phenomenon occurs in the process of hypersonic inlet start, which has an important influence on the working range of the scramjet. In this paper, a hypersonic inlet is introduced, and the inlet hysteresis caused by variations of angle of attack is studied by experiment and numerical simulation. The experiment is conducted in a free-jet wind tunnel LF-220 of NUDT (National University of Defense Technology) at Ma=5.0. The regenerative electric heater is used to heat the high-pressure airflow. The total pressure in the settling chamber is 1.59MPa, and the static temperature in the test section is 91.67K. The model is constituted of the first part of forebody, the second part of forebody, the cowl and the lampstand. The pressure sensors are used to measure the wall pressure at a frequency of 100Hz. The dynamic process from unstart to start with the change of angle of attack is captured in the experiment, and the self-starting/-unstarting performances are obtained. The results show that a significant hysteresis occurs in hypersonic inlets with the change of angle of attack. In the experiment, the self-starting angle of attack is -1.3°, while the self-unstarting angle of attack is larger than 10°. In the study of the self-starting/-unstarting process, it is found that the angle of attack and the large-scale separation zone alternately dominate the mass flow.