Symbol is one of the cores of GIS and mapping system. However, difference of design styles, data structures, storage methods and render strategies among the systems leads to no synchronous sharing of map symbols when sharing geographic data. Taking map symbols as a breakth-rough, the paper analyzes and compares the ArcGIS symbol model with the SLD and provides the mapping mechanism between ArcGIS symbols and SLD symbols to study the symbol sharing between them. The analytic result shows that the SLD symbols all can be converted to the ArcGIS symbols, but only small part of ArcGIS symbols can be converted to the SLD symbols. The ArcGIS symbol system is more consummate but not perfect and the closed symbol format goes against to symbol sharing. And the SLD symbol format is open, but it is too unitary to meet the needs of Cartography. Therefore, a common symbol model is required to synthesize ArcGIS symbols and SLD symbols to achieve the map symbol sharing.