Abstract: Based on the properties of wideband source's spatial spread, an algorithm for reverberation suppression in beams domain is proposed. In an effective observation range, a compact bank of receiving spatial beams is operated to transform the data from element domain to beam domain. Angular Distribution Index (ADI) is obtained by comparing to a reference value which is computed by Monte Carlo Integration. ADI decreases with a stronger target echo. Hence, choosing an appropriate threshold of ADI, the target echo can be separated from reverberation by cutting off the high AD components. The filter is compatible with the procedures of beamforming and detection for the current sonar. The computation complexity of the filter is low. The relationships between ADI and frequency, bandwidth, signal- reverberation ratio, are illustrated by a simulation example. The processing results based on the lake-trial and sea-trial data show that reverberation can be significantly suppressed, and threshold choosing for wideband ADI filter is fault tolerant.