Abstract: The six degrees of freedom(6-DOF) excitation platform is an important ground apparatus in the multi-axes vibration environment simulation. Because of its complex structure and multiple degrees of freedom of motion, it is difficult to build an accurate structural dynamic model. Based on the structural dynamic characteristics of the 6-PSU platform, a parametric modeling and model updating method is proposed. Firstly, the joints and the moving parts are regarded as the model modification objects, since they have their contact interfaces included in the bearings and the linear guides. And their equivalent dynamic models could be established with the proposed decoupling method for their stiffness and mass. Secondly, on the basis of the equivalent dynamic model, the beam cross section parameters for the structures of the joints and the moving parts are updated by using of the structural modal information. After that, the contact stiffness coefficients are revised using the frequency response function(FRF). Through the above steps, the updated finite element model for the 6-DOF platform is built. The comparison between the calculation based on the model and the FRF test show that the modeling approach is effective and valid.