How to use the intuitive graphics to reflect the original landform and topography and alteration to control construction progress and quality in construction of waterway dredging is important and difficult in the construction process.Based on a 2D graphics by CASS digital,combined a 3D graphics by Surfer software,the underwater topography is analyzed.The method can fully develop the superiority of 3D model in post bathymetric surveying and mapping,and the satisfactory result is achieved.