In this paper, according to the field inverstigation and relative informations, the auther analysis and studies the characteristics of physical geography and the factors of land differentiation in Ankang District, and presents a principle of classifing land in mountain area, delimiting the identified index of each type and the system of land classification. In addition, from the Point of view of dialectical materialism and synthetical study, the paper expounds the features of various type of land and makes different potential valuation,In order to make people scientificially understand complex natural environments in mountainous area and manage better agricultural production, the author suggests a way to use rationally each type of land.