The evaluation of the dynamic behavior of a rotating system on a machine tool is possible by means the modal parameters. A mixed and experimental approach is used to identify the modal parameters of a specially-designed test rig The modal identification os done both for nonrotating as well as rotating systems. These modal parameters are used to validate a developed Finite Element. It is the aim of this paper to identify the modal parameters of the rig in several stages if its mounting on the test stand. In the case, the modal parameters provide us the necessary information to adjust gradually the mathemathical model.