The mineralogical composition of a soil catena of dark brown forest soils derived from granite in the Xiao Hinggan Mountains was investigated is relation to weathering proccess under the conditions of warm-cool humid climate and the different relief.It was found the acid eluviation proccess in soils was getting weaker from the upper slope downwards under the bioclimatic condions mentioned above.The minerals were generally weathered in the following sequences:biotite acid-weakly acid dioctahedral Al-(iaterlayer) vermiculite weakly acid-neutral secondary chlorite; plagioclase and microcline weakly acid mectite or interstratified minerals of smectite-kaolinite group.