The Auto Target Recognition (ATR) has been used to solve the problem that the huge data flows provided by a high speed image acquistion system are not easily transferred and stored,in which the key is how to find the Region-of-interest (ROI) of a target quickly and exactly.To detect the ROI of the target,a morphology Haar wavelet method and a mathematic morphology are combined to use in the ROI detection and a new target ROI detection operator is designed. An image is decomposed with morphology Haar wavelet,then the new ROI detection operator is used in the field of scale signal decomposed by morphology Haar wavelet to find the ROI of target.The simulation results indicate that the highest detection ratio of the ROI can reach 1.000 0 and the lowest false alarm ratio of the ROI only is 0.001 2.Moreover,the time consumption is only 10-1s for a image with a pixel level of 102×102.In comparison with traditional algorithmns,this method can find the ROI of the target effectively and can save the time consumption and hardware resource.