Abstract: With correlation and spectrum analyses for surface topography, the concepts of relative waviness and effective waviness,relative wavelength and effective wavelength are introduced in this paper. It is pointed out that the technology of correlation and spectrum analysis is an important and useful tool to study the effect surface topography on lubrication. When the relative waviness comes into effective waviness, the effects of both wavelength and amplitude on tribological behavior should be considered. But, when relative waviness comes into roughness, only the amplitude effect of surface topography should be considered.