Abstract: Rainfall has a significant meaning in urban afforestation, flood control, drainage and agricultural production. The experiment used artificial simulation of rainfall indoor to collect soil moisture content data through TDR. The influence of different rainfall intensity on water infiltration in vertical one-dimensional was investigated to understand the characteristics of soil moisture migration and wetting front movement and soil moisture redistribution in the rainfall condition and than to find ont the optimal soil depth scope for water preservation. The results showed that after the rain, soil moisture re-distribution is mainly controlled by soil water potential at the beginning, but it becomes dominated by evaporation with the time. The research showed that the optimal water preserving capability layer in sandy loam soil used in the experiment is between 20-35 cm.