"OneGeology" is an international cooperative project which makes it accessible to share the geological map database on the internet aiming at creating a global geological map database at the scale about 1:1000 000. "OneGeology" system is a distributional system based on WebGIS technology. Every data provider can manage their data on their own Web server. The "OneGeology" portal accesses all of distributed web servers and displays the information. In this article, we took setting up of China 1:1000 000 geological map Web Map Service (WMS) as an examlpe, and implemented the methods and flow of WMS based on the research on MapGIS formate data. There are multi-methods to implement WMS. We used open sources MapServer and Apache software to serve our WMS. MapServer can publish ESRI'S Shapefile, so we need to transfer MapGIS file into ESRI'S Shapefile. Because symbol system library in MapGIS including 3 types (point, line, polygon) can not be used in ArcGIS platform, it must be built in the ArcGIS platform and symbolise the spacial data according to the attribute data. MapServer configures its web services by text configuration called "mapfile", which is the major delivering contents of geological map data and includes map service data sources, data output format, symbolizing type, and metadata information, etc. At last, each provider registers in "Onegeology" potal to offer serves for WMS.