Abstract: The control methods of large-scale separated flows inside a low-speed axial-flow compressor facility were investigated by external acoustic excitations.The focus of research was put on the coupling relationship between excitation frequency and typical shedding frequency of unsteady separation vortex,while the influences of excitation amplitude and the types of the excitations signal wave on the flow control were explored.The experimental results indicate that the excitation frequency and excitation amplitude are the most importance parameters for controlling large-scale separated flows.The types of the excitation signal wave has some effects for separated flow control too.When the unsteady excitation was the most effective frequency with proper amplitude,the large-scale separated flow was delayed or controlled,and the flow field became more regular near the compressor's stall margin.