It is an indisputable fact that rainfall can induce landslides in loess area; however

groundwater levels are always very deep in loess area. At present

it is not clear that how does rainfall move in loess and whether it affects groundwater directly when infiltrating ground below. In order to simulate the natural rainfall condition

manual drip experiment is carried out. By using soil moisture meters which are inserted into the wall at a 10 m-deep exploratory well

the changes of moisture content with time of soil layers at different depths in the process of artificial rainfall infiltration could be easily observed; the range affected by rainfall could be confirmed later. The result shows that moisture content of soil layers within 0.5 m changed obviously when the precipitation is 3.82 mm/d (light rain)

while that of below have almost no changes; the moisture content within 1 m increases when the precipitation is 10.31 mm/d (moderate rain); the moisture content of the layers within 1 m increases significantly

and that of between 1 m to 1.6 m have a slight rise when the precipitation reached 25.21 mm/d (heavy rain)

the changes of moisture content lag and the growth decreases gradually with depth. It is shown that if there are no obvious water paths in arid loess region

the infiltration depth of short-term rainfall is limited and it is difficult to reach the groundwater level

but according to the results of paleosol in deeper

the moisture content of paleosol has a considerable increase even though that of upper loess is relatively weak

which indicates that unsaturated seepage or vapor migration do exist in loess. It is also found that the circulation of soil moisture is primarily occurred in evaporation zone; that within shallow 0.7 m in Longdong Loess Plateau

if there is no recharge from follow-up rainfall

the rainfall infiltrated within evaporation zone will be excreted upward by evaporation; however

it will continue to move downward without the influence of evaporation when infiltrating beyond the evaporation zone; the water will gather on the surface as encountering the impervious layer

which is also reflected preferably by finite element simulation.