This paper presents a design for a magnetic levitation absolute-vibration test system which can be used by vehicles to measure the road surface roughness. The relationship between the vibration test system output voltage and measured speed of the object was obtained through testing, the power spectrum of the measured signal was obtained by virtual instrument analysis, the vibration waveforms of the vehicle over gentle and steep slopes were measured respectively and the road surface roughness was obtained by waveform analysis. Data was saved where the waveforms exceeded threshold. Finally, the steep slope was located using a GPS system. Experimental results show that the magnetic levitation absolute-vibration measurement method has characteristics of high sensitivity and a wide frequency range. This lays the foundation for research into multi-dimensional vibration measurements through magnetic levitation vibration test systems in vehicles.