Abstract:Aimed at the existent one - sided and wrong ideas and action of many enterprises inpurchasing CAD systems, and based on the comprehensive analysis of large amount of materi-al, the author points out the causes which result in the failure in purchasing CAD systems.The principles of purchasing software and hardware are raised. That is basing on practicalityand advantage, not on pursuing "new and full", high - leve and high - grade blindly. Theauthor also puts forward emphatically the importance to consider the background of thesoftware corporations and suppliers, the capabilities and functions of software, and the abilityof being easily leamed and used. It is discussed in detail that why the national computers of fa-mous brand should be chosen as host computCrs and why the mainstream CPU should bechosen. In this paper the author also puts forward some original opinions about the embezz-led software and the system of scanning input for enginecring drawing. Valuable suggestionsare given to establish CAD network system.