The 3D geological modelling is an important field of research [1]. Unfortunately the variety of the input data makes the fully automatic building of geological model difficult. In this abstract we will present a new approach implemented in the GOCAD software (GOCAD is a 3D modeler developped by the computer science department of the Nancy School of Geology in the frame of an international consortium). This method is baserf on the a.naiysis of the input data, and elementary informations given by the user.