Abstract: By indoor and field simulated experiments of infiltration and evaporation of the rainwater,the paper studies the depth and velocity of infiltration and the daily evaporation.The result indicates that the effects of different rainfall amount on depth and velocity of infiltration are significant.The preserved time of rainwater in the sand soil is different.It spends 4,6,11,15 d to evaporate rainwater of 1,2,5,10 mm.Apart from some evaporated,a part of the 15 mm rainwater is kept in the sand soil because of a dry layer of sandland.Due to the great difference of vertical distribution of the various plant roots,the more rainfall and the deeper the infiltration,the more rainwater can be used by deep-rooted plants in a longer period.