Abstract: Three-dimensional Buffer Analysis is one of main functions of 3D spatial analysis, further, is one of important parts of 3D geographic information system(GIS). It should be improved for buffer analysis of boundary representation(B-rep) of spatial objects. This paper proposed a method of buffer analysis based on spatial tessellation. Today, buffers of B-rep always are presented by volumetric body, which are redundancy, lack of accuracy and poor visualization. For solving these problems, firstly, B-rep is voxelized to volume. Secondly, Signed Euclidean Distance is to select available voxels. Thirdly, Iso-surfaces are extracted by implicit algorithm. Fourthly, buffer surfaces are reconstructed by discrete smooth interpolation algorithm based on Buffer Points and Iso-surfaces. Finally, a group of tests were carried out for comparisons in aspects of time complexity, visualization and equidistance between paper's method and volume model. Furthermore, both inner and outer could be realized. As the above discussed, experiments show the method in this paper are universal and extended.