Swath bathymetry system surveys with wide swath, high location resolution, and is used to detect sea bottom terrain. But the object resolution detected decreases as the depth increasing, its data processing with high mistake, used rarely in sea floor object survey.So GeoSwath, a multibeam sonar does. Although it covers an angular range of -120°to 120 °from the vertical direction, providing high density and high quality bathymetry data along with side scan like amplitude imagery, the data processing is more relied on human intervention to get accurate depth contour and sonar image which prevent its propular use in survey of seafloor targets. The purpose of this article presents survey parameter setting during survey and data processing technique to survey seafloor target by GeoSwath system, which set the proper detect parameters including ping length, ship velocity to increase the points over targets, setting navigation line parallel to the maximum dimension of target during survey, adopting appropriate filter to depth data processing and using TVG control over amplitude data to get accurate depth grid and sonar image of seafloor target. Finally, the way is used to measure the artificial object in harbor and two ship wrecks at sea, compound with the sonar image taken by the forward looking sonar, to search the ship wreck near harbor, to help to recognize the targets and locates its real position. This technology improves GeoSwath survey capability with compound detection and is helpful for make precise map for waterway. Also this work is helpful to achieve detecting seafloor objects fast, accurately, effectively in underwater large scale area during salvation and rescue task.