Abstract: The outputs of sonar beamformer represent the target power information in all directions and the peak position of directivity is used as the target's approximate azimuth. It is necessary to find an appropriate parameter, which is sensitive to the tiny change of azimuth, to obtain accurate target's azimuth. The phase difference in every azimuth given by two sub array can be used to estimate the azimuth close to Cramer-Rao low boundary, and the accuracy of direction finding of sonar system can be obviously improved without much operation. So far the half beam processing technique of split-array has been widely researched and applied. The different applications of this technique in underwater acoustics equipment, such as the wideband cross-correlation detection in passive sonar, phase binning processing in active sonar,HBF and ADT with variance of phase difference, are mainly discussed and summarized in this paper with principles, processing flows and results.