The 3D terrain visualization of coastal zone is based on the seamless integration of geospatial data from water to land. Because of the differences in surveying methods and application areas, the land elevation data and the water-depth data are different in spatial reference, data accuracy and data type. This paper presents a methodology to integrate multisource terrain data of coastal zone and build an integrated DEM from water to land. Based on the C++ and OpenGL, this paper offers a 3D visualization system which realizes the realistic 3D terrain visualization of coastal zone with the instantaneous shorelines generation.