The invention relates to a method for obtaining geometrical parameters of typical terrains in a digital map. The method includes the steps of terrain classification and recognition, terrain simplification, extracting of the geometrical parameters of the terrains and the like. According to the digital map in the GeoTIFF format in the ASTER GDEM type, by means of an ArcGIS tool, the normalized elevation, the normalized gradient, the normalized gradient variability, the normalized curvature and the normalized terrain undulation are calculated, iterative selforganization (ISO) unsupervised clustering is carried out with the obtained parameters as characteristic indexes, and the preliminary classification of the terrains is obtained; then the terrains are classified into the plain, the hill, the low mountain, the medium mountain, the high mountain and the like according to the average undulation of the various terrains; the geometrical parameters such as the positions, the bottom faces and the heights of the typical terrains are finally obtained. The method has the advantages of being feasible and practical.