Abstract: Respectively for each type of Euclidean distance, namely the maximum distance, the minimum distance, the average distance and the centrobaric distance, recursion formulae of distance between micro-structure parameters are deduced based on the pedigree cluster principle. Afterward, pedigree cluster method and corresponding process for clay micro-structure parameters are put forward to classify geometrical characters, and anisotropy coefficient is defined to evaluate significance of geometrical anisotropy. Studies on some SEM photos, taken in horizontal, vertical and 45o inclined planes from a layered soil sample, show that the anisotropy coefficient calculated by the average distance method is almost the same as that by the centrobaric distance method. In addition, the conclusion drawn by the pedigree cluster method is consistent with that by the principal component analysis method, and it illustrates that the geometrical anisotropy of the layered soil is distinct.