The multi-scale representation of spatial data is one of the most important and difficult problems in the field of GIS. Digital Depth Model (DDM) is the digitized model reflecting the depth change of ocean. As an important representation mode of sea floor relief, DDM is not only the main source information guarantying safety navigation, but also the information platform for marine geoscience research, maritime engineering, subaqueous archaeology and so on. With the development of marine geographic environment, the application fields of DDM are expanding increasingly, which results the requirements for multi-scale representation of DDM. In fact, in the same sea area, DDM of different scale is the different digitized representation of the identical sea floor landform. Therefore, it is an effective approach to multi-scale application by studying a multi-scale representation method based on original DDM. As an important visualization representation mode of digital depth model, bathymetric contour shares the same constraint multi-scale representation principle of DDM. Existing multi-scale representation algorithms of DDM are mostly by dimensional extending of generalization algorithms for two dimensional bathymetric contour graphics. For those multi-scale representation algorithms barely focus on the geometry characteristics of DDM, and simplify DDM just by deleting some grid points and reserving the feature points. While DDM generalization is not a simple process of accepting or rejecting the grid points of DDM, some factors including geographic and scale character of DDM should be considered to maintain the consistency of spatial cognition and abstract grade. Mainly focuses on the geographic and scale character of DDM, based on the analysis of the essential principle of the two dimensional rolling circle transform algorithm, and by means of rolling circle transform dimensional extension, the paper has brought forward a multi-scale representation of DDM based on rolling ball transform algorithm. Namely, by using different size of three-dimensional ball instead of planar circle rolling on the upper surface of DDM, which will preserve the positive relief of DDM and reduce the negative relief of DDM contrarily, and realizes the multi-scale representation of DDM from the viewpoint of guarantying safety navigation. Besides, the paper also expatiates the keystone and solution steps of the algorithm. At last, under the condition of VC++, some experiments have been done to validate the algorithm's validity. The experiments show that the algorithm could preserve the basic characters of the DDM, meanwhile, with high computing efficiency.