As an important support of parts，column plays a very key role in the final gear grinding precision.The combination column was designed based on unitary column to improve the installation and positioning accuracy of gear grinding machines column. The inherent frequency and the vibration shape parameters were got through the modal analysis of the combination column and a single column, and stable grinding vibration situation was got between the two through harmonic response analysis. By comparing and analyzing, it proves that the combination column is better than unitary column in structural dynamic stiffness and vibration performance.It provides the corresponding theoretical basis for further optimizing the gear grinding machine column and improving the machining accuracy.