Abstract: To detect stall inception signal before the whole compressor running into deep rotating stall,a method based on averaged numerical difference is developed to detect short length scale disturbance.While the method is used to analyze measured pressure data of certain axial flow compressor, corresponding analysis results demonstrate that the method can detect stall inception signal of the compressor 0.02～0.05 second before the start of deep rotating stall,and that the method has certain engineering application value.