Abstract: An investigation on buzz in an axisymmetric external compression inlet and its control are presented.A zone of boundary layer bleed on the cone surface at throat has been designed（Fig.1）.A block diagram of a dynamic pressure measuring system employed is shown in Fig.2.The static pressure fluctuation on the cone surface at throat has been picked up by Kulite transducer.The results of the experimental investigation can be summarized as follows:1.At Mach number M∞=1.97 and angle of attack α=0°,there is only a little static pressure fluctuation in the stable supercritical regime or subcritical regime with a bow shock attached ahead the cowl lip.When the bow shock is away from the cowl lip,the feature of unstability appears.And as buzz occurs in the inlet,the pressure fluctuates sharply（Fig.3）.The characteristic frequency of pressure fluctuation is 43.75Hz（Fig.4）.Its ΔPr.m.s.is about several times that of the supercritical regime（Fig.4）.2.At M∞=1.97,and α=12°,as buzz occurs in the inlet,the bow shock on the lee side of the cone vibrates sharply with a large amplitude（Fig.6）,and the pressure fluctuation is more sharp than that on the windward side（Fig.7）,and its main frequency is 18.75Hz（Fig.8）.The Δpr.m.s is about double that on the windward side.The bow shock on the windward side vibrates with & small amplitude（Fig.6）,and the main frequency is 20Hz.3.By opening bleeder door with mass flow ratio Wbi/WG=0.0061,the inlet buzz disappears at once.The bow shock becomes stable（Fig.10）,and the amplitude of the pressure fluctuation and their ΔPr.m.s.become smaller（Fig.10 and Fig.11）.The main frequency of pressure fluctuation,for example,on the lee side disappears（Fig.12）.