This paper introduces the methods of automatic inquiry and mark for dimension tolerance used in mechanical CAD of AUTOCAD,and presents a practicable software for dimension tolerance mark developed according to the National Standard(GB1800-1804-79)

• 介绍了AutoCAD环境下机械CAD的尺寸公差自动查询和标注的方法 ,给出按公差与配合的国家标准 (GB180 0 - 180 4 - 79)开发的尺寸公差标注系统实用软件。