Coastal zone geographic information is coastal zone spatial data including remote sensing images, digitized maps or charts and various surveying and statistical data. With the development of Digital Earth, coastal zone geographic information is changing from plane, static and isolated to three dimensional, dynamic and associated. However, there is no comprehensive, compositive and dynamic study on processing of coastal zone spatial data. Mathematics base is the basic study on multi-expressing of coastal zone geographic information, which includes coordinates system and projection system. The influence of geodesy surveying datum system is expressed through the plane coordinates system and vertical datum system. According to digital maps, remote sensing images and three dimensions terrain sight, there are three typical projections: static map projection, dynamic space projection and three dimensions perspective projection. The mathematics base can be unified to ellipsoidal geographic coordinates. Coastal zone geographic information multi-expressing system (CZIMS) is explored in VC++ programming language, and the integrated structure of CZIMS is discussed. The key technologies including coastal zone vector map display, remote sensing images processing and three dimensional terrain building are studied. The system is developed to provide real-time, dynamic information and multianalysis for coastal zone monitoring and management.