Based on the principle of pedigree cluster, recursion formulae of distance between micro-structure parameters are given. Then, pedigree cluster method and corresponding process for loess micro-structure parameters are proposed to classify micro-structural characters of loess before and after collapsing. The study results indicate that micro-structures of loess before and after collapsing have significant cluster characters. The grain on horizontal section is considered as isotropic. Geometrical anisotropy of the grain on other sections is distinct. The proposed method can evaluate the difference of grains in study field in size, shape, deposition, direct, area distribution and grey distribution.