Abstract: Based on the field experiment, the two-dimensional mathematical model of the relationship between the infiltration and runoff of farmland in the loess region was established. Furthermore, the model was verified with the data of soil moisture and runoff in the different underlying runoff plots at Changwu county, which is one of research stations of Chinese Ecosystem Research Network(CERN). The results showed that the model precison was higher for simulating the soil infiltration and runoff during the rainfall process and the soil moisture during the evaporation after rainfall. The model was used to simulate the relationship between the infiltration and runoff in the loess region.