Abstract: Based on the energy theory of soil water,this paper studied the influence of sand layer in loess column oninfiltration characteristics by laboratory experiments and mathematical simulation. The results showed that sand layer embedded in the loess soils is characterised not only by improved water-tightness, which can make infiltrationflow stay on sand layer in soil body to a certain limited exent so as to improve water detention capacity in upper soillayer,but also by decreased infiltration flow and wetting velocity, which convert the non-linear process of infiltra-tion into the linear process, thus rendering the whole infiltration process to enter into the stable infiltration stagewith a smaller infiltration rate. Accordingly the results of this paper have provided the theroretical basis for the adop-tation of setting up sand layer in the loess soil as an important engineering practice for the infiltration prevention in the water conservancy work.