Abstract: Dykes are always closely coexisting with ore veins in deposit，and it is of great significance in reveling regional geological evolution process and guiding prospecting work.During the process of geological mapping and geological map synthesis，dyke is often neglected or integrated with general geological unit because of its relatively small exposure scale.In veiw of the loss question of dyke information in geological map synthesis，a generalization method of dyke based on geographical fact during the geological generalization process is put forward.Firstly，based on the continuity principle，the potential homologous dyke groups are identified，through the deduction of geological evolution process，the homologous judgement of dykes is conducted and dykes are amalgamated preliminarily.Then，based on the square root law，loading capacity and area threshold of the maps with different mapping scale are calculated，so as to determine dyke retention or abandonment.Finally，the outer shape and internal construction of dykes are simplified，so as to avoid the adjacent conflict problem between dykes and other geological units in the process of mapping scale transformation，therefore，dykes generalization process of geological map is realized.The comparison results of test and existing geological maps with small scale show that the proposed automatic dyke generalization method is more reasonable，the dyke integrity can be effectively avoided under the condition of retaining the stratigraphic lithological characteristics and geological tectonic characteristics，and the generalization process is less affected by human factors.The above study results further indicated that a new ideal for the processing of special geographical elements during the generalization process of geological maps is proposed.

Key words: Cartographic generalization, Dyke, Geological evolution process, Special geographical elements, Square root law