Precipitation infiltration testing of Loess Plateau areas indicate that precipitation occurs with evaporation during its infiltration but doesn't reach phreatic water level. Deuterium and oxygen isotopes in soil water are similar to that of groundwater, indicating that soil water comes from groundwater. External water is important water supply for rivers and lakes in Loess Plateau areas, whereas local precipitation may supplement partially to them during flood seasons. The underground watershed is basically overlapped with basement faulting zone in the loess region of Ordos basin, indicating that the underground water may originate from the basement faulting zone. Clusters of grains formed by deep circulation water gives rise to continuous eolian deposits. Therefore, deep circle underground water is a necessary condition for continuous accumulations of loess. Based on the aterial unbalance of CaCO3, no calcium tuberculosis slice and high uniformity of 13C/18O isotope, we can deduce that the secondary carbonate minerals are also carried up by upwelling groundwater, not precipitation infiltration. The investigation shows that the scale of loess tableland is proportional to water recharge from basement fault. Particles of dust loess plateau are accumulated symmetrically along the faulting zones. The more upwelling water, the more particles accumulated, resulting in increasing scale of the plateau; whereas faulting with small amount of upwelling water is responsible for the formation of soil hills and mounds.