By taking the formation of mud-rain and dust-rain and other mud "granular fine sand", and the inlaying of fine mineral grain into coarse sand and other phynomena, as the sole characteristic for the formation of loess plateau caused only by the blowing and carrying of wind, and after checking each different periods'loess,which were formated for 2.5 million years long, it was believed that the formation of the loess plateau was indeed the causes that the loess dust, which was carried by wind from west, met the moist airflow from east then continuously fell down then accumulated gradually. The loess layer accumulated this way, in which the structure appears frame touch, possessed fine aeration and permeability originally, later it is affected by the reproduction of vegetation, especially by the effect of root system of grass, the cha racter is strengthened. This is the sole background and source for the accumulation of loess up to 100 meters and formulating the complete loess plateau--ancient soil under the natural condition. The soil and water loss violently, the main reason was human's destroy on natural vegetation, thus it thoroughly destroyed the permeability and anti-scouring of soil. So recent harnessing measures on loess plateau are forced to be "no-site-retain all precipitation" as the strategic goat and adopt measures as "cereal crops are planted on plain and plateau land, forest and fruit tree are set on gullies, grass and shrub are located on hillside";and combining with the social and economic requirement, to arrange the reasonable land utilization and concrete productive measures.