In the five types of soils on the north slope of the Shennongis Natural Conservation area, 2:1 type clay mineral was predominant, and there were few kaolinites. There existed a weak desilicification in the soils. For the yellow-brown soil and mountain yellow-borwn soil, the main clay mineral was hydromica, and there was a certain amount of vermiculite, as well as a few 1.4nm intergrade minerals and kaolinites. In the mountain brown soil, mountain dark brown soil and mountain brown coniferous forest soil, 1.4nm minerals (being mostiy 1.4nm intergrade mineral) were the major clay minerals, and there were certain amounts of hydromica and chlorite and a few kaolinites or vermiculites. For soils examined, the higher the sampling site, the stronger the eluvial depotassification process of clay mineral in soil was. The contents of various noncrystalline iron, aluminum oxide, increased obviously with increasing altitude in the area. The enrichment of noncrystalline iron and aluminum in case of higher altitude, which could play a main role in influencing the surface properties of soils, resulted mainly from the leaching losses of base and silica under the conditions of low temperature, high moisture and the complex or chelation eluviation of organic acid.