Vibration mode of vertical milling machine, especially dynamic performance of machinetoolworkpiece system can affect workpiece quality and processing stability directly. Currently, the frequent response functions of the tool and the workpiece were obtained by exciting the tool and the table. And the superposition method was used to acquire the relative frequent response function of machinetoolworkpiece system. The method above can get precise amplitude spectrum, but the phase difference cant satisfy the engineering problem. To solve the problem, a new relative excitation method was proposed. The method can obtain precise relative frequent response function of the machinetoolworkpiece system, and the dynamic feature of machinetoolworkpiece system was analyzed. The results implies that the tool FRFs is consistent with the dynamic compliance of machine tools from the globe aspect. Whereas, there are much difference in the high frequency range of the direct and cross FRFs Gxx and Gyx, and the low frequency range of the direct and cross FRFs Gyy and Gxy.