The invention discloses a multi-beam bathymetric chart construction method based on seabed digital depth model feature extraction. The method comprises the following steps: constructing a DDM (Digital Depth Model) based on original multi-beam sounding; establishing a slope and second derivative composite model based on the DDM; extracting feature points based on DDM sub-blocks; inquiring original multi-beam depth based on the feature points; comprehensively making a multi-beam bathymetric chart based on a graph layer. By the method, depth points which can represent the basic features of seabed topography are extracted quickly based on the DDM in a blocking mode, then a query radius is set based on the coordinates of the feature points, a point which is closest to the query radius from original depth data, and a model is re-established, so that the defects that the original multi-beam depth data volume is large and the features are difficult to extract are overcome; the disadvantages that the original sounding depth is difficult to reflect accurately by directly using DDM depth points or central beam points are also overcome. The method has a very important practical application value in seabed topography mapping, hydrographic surveying and charting, marine information systems, computer graphics and seabed scientific research.