The topography of inland waterways is complicated and changeable,and the traditional way of topographic survey is heavy workload and inefficiency.We apply the ship-borne 3D laser scanning system to get the large-scale terrain data.Taking an inland waterway as an example,we summarize the key steps in the digital mapping,and analyze the accuracy of the experiment using the verification point of collected by RTK.The results show that the precision of point cloud that is collected by ship-borne 3D laser scanning system is superior to 10 cm in plane and height,which satisfy the demands of large-scale mapping accuracy.