Sanchuanhe watershed is one of the eight key integrated control areas of soil and water conservation in China, As the developing of control work and agriculture forestry and animal husbandry, soil of farmland is required more and more highly, This paper evaluates soil fertility of every type farmland, using PCA method, based on the investigation and measurement of soil fertility of different farmland in the watershed.A new classification of farmland has been suggested, It proposes scientific base for the regulation of different type farmland and. the development of ag-riculture.