Abstract: The design of software of surface symbol has promoted the development of thematic auto-cartography. The software is possessed of the character of serial structure in using these programs. It is composed of subprogram of surface symbol, of computing sign coordinate and of plotting out independent sign. By using the software we can design different signs of quite a lot of different thematic maps, and can automatically plot them out.The realizing process of surface symbol subprogram includes transformation of coordinate of polygon, interpolation computing of terminal point, arrangement of coordinate terminal point and recovery of system of initial coordinate, etc.To achieve the process of subprogram of computing sign seat coordinates, it is necessary to define the orientation of the drawing pen in going forward, to compute how many signs in a row and to define coordinate of every sign under the left side, etc.The besal designing mind of subprogram of independent sign is that it has arranged a data district that will store digital information of initial address of sign of every kind. Increment of coordinate is computed in the program,and coordinate value of drawing pen in advance is computed in the program too. The purpose is to plot out sign of different figures. By using different data it is possible to plot out sign which can reflect quality diversity of geographical regions or feature of numerical value.In a word, the study of software provides certain technical and scientific methods for thematic auto-cartography of agricultural map and population map, etc.