Based on the long-term experiments of different cutting frequency of natural vegetation (Imperata cylindrica var. major), in red soils of south of Hunan Province, the changes of contents of organo-mineral complex, acidity and Fe, Al oxides were studied. The results showed that the changes of the soil acidity were not any regular, but the contents of organic matter, organo-mineral complex, exchangeable K, amorphous Fe and Al, complex Fe and value of loosely combined/tightly combined, activation degree of Fe in the soil had a tendency of increasing, whereas the contents of exchangeable Na and Ca, free Fe and Al were decreased relatively when the cutting frequency treatments from one year to 6 years.