The effect of the sand layer position in layered soil profile on
the phreatic evaporation rate was researched through the
laboratory simulating soil columns indoor. The mechanism was analyzed and the quantitative relationship between the evaporation rate and the sand layer position was discussed. The results showed that the sandy soil in layered soil profile can stimulate or obstacle the water movement as compared to the uniform loam column with 50cm depth of water table, this was mainly determined by
the position of the sand layer. When the distance between the low boundary of sand layer with 5cm thickness and the water table is zero, the evaporation rate increased with 10 - 20% ratio. When the distance is more than 5cm the rate started to decrease, and the rate decreased with 70~80% ratio for the sand layer soil column with 35cm distance. The rate keep relative steady when the distance was more than 35cm. This changes outlined above were determined by the hydraulic conductivity of the sand layer and the relative size of hydraulic conductivity of these soils in layered soil profile. Finally, the functional relationship between the accumulative evaporation and sand layer position and evaporation duration was developed. The equations are important for forecasting the effect of sand layer on evaporation rate and calculating the proper sand layer position, which made the evaporation loss is least.