Abstract: It is of great importance, dynamic modeling and analysis, for structural design and performance analysis of mechanical systems. The adoption of convenient dynamic modeling methods and ideas can quickly build the system dynamics model and provide a foundation for the subsequent research. In order to build the dynamic model of multi-component mechanical structure quickly, the influences of two kind of different generalized coordinates on the modeling process was analyzed, and the consistency of the two dynamic models was verified. In order to simplify the stiffness matrix form, the linear feed system and the machine tool dynamic model were established with the relative coordinates as the generalized degrees of freedom, and the reliability of the model was verified based on the natural frequency. The results show that the dynamic models obtained by the two modeling ideas are different in form, but the results are consistent. The dynamic model of the whole machine can well predict the first natural frequency of the system, with an error of 3.16% compared with the measured value. It can serve as a convenient model for the optimization of low-order natural frequency, and can quickly complete the optimization and allocation of mass and stiffness.