Vehicle vibration is caused by road roughness. When wavelength and amplitude are at the same level and the road surface waveform is different, the vibration waveform can also be different. When vehicle-road interaction is strictly analyzed, it is necessary to divide the vehicle vibration data according to the type of road surface waveform. The lifting scheme theory, which is based on the wavelet transform, was used to consider the road surface waveform detection method, which is influenced by the unsprung mass vibration of a vehicle. The basis function used optimizes the shape corresponding to the analysis purpose, based on the spline function. This method can accurately monitor the unsprung mass vibration of a "convex" type waveform of high magnitude.