Abstract: For the difficulty of estimating damping ratios in the dynamic design of aeronautics engine compressor blade,a response model of rotary blade under distributing excitation was established,and a nonattached damping ratios testing method with distributing excitation unloaded instantaneously(DEUI) was developed on the basis of this model.The former eight resonance damping ratios were tested with DEUI as well as with half-power method and modal analysis method,while the correlations of their experimental results were analyzed.It shows that the correlations between DEUI and the other two methods are more than 75%,and without interferences of frequency resolution and power spectrum analysis error,DEUI is more accurate.