Abstract:By taken the Cincinnati 750 as an example, the dynamic characteristics of the three-axis vertical CNC boring-milling center were researched. When a model was established in accordance with the analytical method of finite element model (FEM), modal analysis was then conducted to obtain characteristics of each vibration mode of the machine tool, and the weakness in structure of the machine tool thereby was located. One point on the weak part was selected to perform harmonic response analysis, and the maximum excitation force error of the machine tool and its corresponding characteristic frequency were calculated. The results show that with relatively large displacement of the spindle box, resonance is prune to occur when frequency of the excitation force approaches natural frequency of the 10th mode of the machine tool structure.