Abstract: The problem of the filtering technique for three-dimensional surface topography is dealt with in this paper. The frequency characteristic of the two-dimensional digital filter which is used to filter the three-dimensional surface topographic signal is analysed and derived. The corresponding high pass and low pass digital filters are designed. Finally, a grinding surface is measured and the topographic signal is filtered respectively with high pass and low pass filters.Thus,the three-dimensional roughness and waviness are obtained.