Abstract: As the pre-processing function of FLAC^3D is weak,a method of model transformation from AutoCAD to FLAC3D is put forward，the modeling process will be transferred to AutoCAD with stronger capacity in modeling.The core idea of this method is to disintegrate AutoCAD model into rectangular units and to import unit data into FLAC^3D.Implementation procedure is as the following:To set up model grouping in AutoCAD and the minimum unit limited sizes,the Boolean operation is done among various groups of interval models.After that，the Boolean operation is done between rectangular units of interval dimension and interval models.If the results of Boolean operation is rectangular and has only one piece,then calculation can be ended and saved.If not，then the interval will be disintegrated into eight sub-intervals and models of every interval will be re-calculated until the dimension of interval is smaller than the minimum unit limited sizes.The next step is to extract 3dsolid object vertex coordinates in rectangular form from the disintegration.Disintegration units and coordinates of various intervals will be collected and saved to summary file.Data like coordinates，units and subgroups will be written on the file with suffix .FLAC^3D.In the end，FLAC^3D will lead in grid by 'import grid' command and the whole process of model transformation is completed.This method is good to design complex models on the basis of non-simplification,improve simulation similarity,lower modeling difficulty,enhance modeling efficiency and further make modeling to be fast and accurate.

Key words: AutoCAD, VBA, FLAC^3D, Model, Transformation, Interval