Using interferometric principle, GeoSwath Interferometric sonar can get bathymetry data and side scan sonar image. There are some differences between the interferometric systems and traditional side-scan sonar. The GeoSwath Plus System 125 kHz was compared with Klein System 3000 in their theory, technical specification, software and test data. The results show that these two systems are different in types of the acquisition data, which leads to the difference in their purpose. The GeoSwath Plus System is more complex, but its applicable depth is shallower. The kinds of acquisition software which can be used in GeoSwath Plus are less, and its post-processing softwares are required more powerful. But there are more choices for Klein System 3000 in its acquisition and post-processing software. It is found by compared the measured data that the position of GeoSwath Plus image is more accuracy, but the quality and resolution of its sonar image are worse than those from Klein System 3000 because of bigger beam horizontal angle and hanging installation.