Summary form only given. X-ray CT (computed tomography) has experienced tremendous growth in industrial application in recent years, and acquiring information about the mechanical parts from CT data has been a great challenge for researchers. This paper presents a new method for the registration of a CT volumetric model of an assembly of parts with a CAD mesh model of a part of the assembly using ICP (iterative closest point) registration method. A few steps to extract feature points should be done as a preprocessing step of the volumetric model and the mesh model before applying the ICP registration algorithm, since the volumetric model and the mesh model are different in their data representation. This preprocessing step is important in order to unify the input of the ICP algorithm, and contributes to the robustness and the speed of the registration process.