Abstract: Based on the digital model which can greatly reflect the actual objects with considering the characteristics of the underground construction process, a new and practical modeling method (CDIM model transformation method) is put forward combing the digital and numerical geological models with relevant structural ones. This method is implemented using the following procedures: (1) cutting the 3D digital model according to numerical domain; (2) extracting control data from the cut model which includes holes to reconstruct the model mesh; (3) forming the numerical model automatically by the attribute; (4) importing the model into numerical analysis system and finishing the modeling work. All the above procedures are carried out rapidly by programming. In the method, the construction process can be simulated conveniently and the complex model can be used in different numerical systems. The present method is proved to be more accurate and simple and the efficiency of preprocessor is highly improved. The transformed model can be used by different numerical systems and provide the best technological support for the construction simulation.