The study on the import of the geometric body by GDML in GEANT4

Geometry Description Markup Language (GDML) can be used as an application interface program to import the geometric body into GEANT4. It greatly simplifies the detector construction work with high reliability. With this mechanism the geometric data of a detector is described in an XML file and read by the XML parser embedded in GEANT4. The geometric structure of a detector is designed in CAD toolkit Solidworks and saved as a standard STEP file. Then, by FastRad the STEP file is transformed into XML script, which is readable for GEANT4. In comparison with the detectors constructed by Constructed Solid Geometry (CSG) provided by GEANT4, those imported by GDML also satisfies the requests of general simulation application. At the same time, some solutions and tips for several common problems during the progress constructing the detectors by GDML are given. (authors)