Abstract: CAD data are a main data source of GIS,and many problems will come forth when they are converted into GIS format,including losing block information,or point feature changed.Through solving key techniques,such as CAD data's semantic translation,block library's communication with common map symbol library,and map symbol's display on multi-platform,synchronous transfer of block information into GIS format in the course of data conversion is realized,CAD block information sharing is achieved.