Abstract: This paper introduces the detecting echo methods for multi-beam sonar.It describes the disadvantage of BDI and WMT detecting methods.So Maximal Amplitude Determining Echo method is presented.It adopts median filter and local variance estimation and wavelet analysis to remove outliers and noises,then one ping data are considered as planar signals and are processed through image processing methods.After high amplitude data have been segmented,accurate and robust DOA and TOA are obtained.The simulated data are analyzed in this paper,and good results are verified.