Based on abundant field investigation and indoor measurement, soil moisture contents were studied at the depth of 0-6 m under different artificial vegetations in southern Loess Plateau before and after the extreme precipitation. The results indicated that in the ordinary year with annual mean rainfall of 600 mm, the average moisture contents at the depth of 1.5-4 m in poplar woods, chinar woods and Chinese phoenix tree forest were approximately 90 g/kg, and the weak drying soil layer hac developed. The average moisture contents at the depth of 4-6 m were about 120 g/kg, which surpass the upper soil layer. Soil moisture contents at the depth of 0-6 m under wheat and lawn fields were good and no soil drying occur. In the year of abundant rain soil drying under all forest vanishes and soil moisture restores well after extreme precipitation, and soil drying was not permanent, which provides necessary condition for good growth of artificial vegetation in the area. But at present, the acceleratory development of ecosystem construction and economic forestry still bring threats to the virtuous cycle of soil moisture in the area, so it should monitor soil moisture chronically, introduce and plant rationally new species in order to obtain economic benefits and meanwhile to realize sustainable development.