An empirical infiltration model,established on the theory of information and entropy,is used to describe rain water added to soil profile. The model shows excellent agreement with the experimental data from field experiments. Contained in the model are three factors,i. e.,precipitation,water capacity of soil and parameter K that reflects soil characteristics,of which the former two are measurable and the latter is defined by trial selection. This model can be used for prediction of soil water,research of soil pollution and evaluatioin of water utilization by crops on farmland.