Design of the dialog box in user application program based on Auto CAD contains mainly interface and driver design of dialog box .Interface design of dialog box focus on meeting the need of searching straight requisite data in user application, inputting conveniently cor responding parameters and selecting pictures .The key of design o f dialog driver is to process user operation , i.e . callback of dialog box .Taking ex ample for interface and driver design of dialog box of two -dimension parametric design of standard parts such as conic roller bearings in the field of machine , a DCL file to define the interface was given .With a user choosing a bearing diameter series in popup list tile, a callback program how to add list elements to list tile was described in details.After the user searched and chose the needed data in list tile , a callback program to display automatically corresponding parameters in edit tile is expounded .