Abstract: In order to explore how the change of attack angle at different frequencies influences the start property of inlet,this paper conducted a wind tunnel experiment for the sidewall compression scramjet inlet with Mach number 3.85 and attack angle at different frequencies.The sidewall compression scramjet inlet,with designed Mach number 6 and start Mach number 2.5,was subject to several flow tests,when attack angle changed from 0°to 8.15° again down to 0°,with the frequency at 0.8,1.6,3.2 Hz and 6 Hz,respectively.Results show that at each frequency,the inlet in a periodic oscillation succeeds to go through a start-unstart-restart process.With the increase of frequency,attack angle gradually goes up in the first periodic oscillation,and sharply goes down in the proceeding periodic oscillation.