The expert system is one of the most important and most active branches of the AI field. It is very significant of its application in the mechanical design to drive the mechanical design process to advance in the automatic and AI direction. Some problems with the study on the drill rig design expert system are reviewed. The main objects and tasks of the drill rig design expert system and their realized methods are discussed. The study is also made on the knowledge presentation; knowledge acquisition and knowledge derivation method proper for the requirements of the drill rig design expert system.