The effectiveneso of the vertical vibration of an automobile suspensio n vibration test rig determines the effectiveness of its excitation. For this re ason, a test for the rig type ACXX 160 was carried out to evaluate its effectiv eness. Four accelerometers were fixed to the platform of the rig for measuring i ts vibration signals in vertical, lateral and longitudinal directions. The analy sis of measured signal into power spectral density function was carried out. On the analysis, it shows that the vibration of the platform is obviously dominated by its vertical vibration as compared to its lateral and longitudinal vibration s; the vertical vibration of the platform is completely dominated by a monofrequ ent component and the vertical vibration of the front beam of the rig is in cons istent with that of its rear beam. The analysis leads to the conclusion that the rig type ACXX160 is effective in its vertical vibration durin g its steady running.