【Objective】The Loess Plateau of China is one of the world’s most severely eroded regions. In this region water shortage is the main limiting factor in agricultural production and ecological environment construction. Therefore, it is of great significance to improve utilization efficiency of the limited water resources in the region to the maintenance of regional ecological environment security and efficient development of green agriculture. The process of soil water infiltration not only determines utilization rate of the limited water sources, such as precipitation and irrigation, but also profoundly affects intensity of surface runoff and soil erosion. Soil water infiltration is mainly affected by soil organic matter content, bulk density, texture, structure stability and soil porosity, water quality and so on. Recent researches have demonstrated that soil surface electric field influences soil water infiltration by affecting stability of soil aggregates and distribution of soil pores. Although quite a number of studies have been reported on water infiltration, water availability and their affecting factors in soils developed from Loess, it is still not clear that how soil interfacial properties (surface electric field and surface potential of soil particles) vary in the process of water infiltration and affect water infiltration characteristics and how applicable the classical soil water infiltration model is when effect of the surface electric field is taken into account. So further studies need to be done. 【Method】In this study, two representative Loess soils, Lou soil and Cinnamon soil, were used. According to the double layer theory of charged particles, the surface electric field of soil particles could be quantitatively adjusted by applying a series of electrolyte solutions different in concentration. Soil water infiltration rate, moisture front migration and cumulative infiltration in the two soils was determined. The Kostiakov model and the Philip model was used to fit the process of soil water infiltration. 【Result】Results show: (1) Wetting front movement, infiltration rate and cumulative infiltration decreased with decreasing electrolyte concentration and increasing surface potential (absolute value), which indicates that surface electric field of soil particles strongly affects soil water infiltration; (2) When electrolyte concentration in the bulk solution was less than 0.01 mol•L^-1 or absolute surface potential value of the Lou soil and Cinnamon soil was more than 233 mV and 223 mV, the temporal variation curves of soil water infiltration in the two soils were close to each other, which indicates that 233 mV and 223 mV is the critical potential value of the soil water infiltration process in Lou soil and Cinnamon soil, respectively; and (3) The Kostiakov model and the Philip model were both applicable to simulating infiltration processes in Lou soil and Cinnamon soil. Further analyses of the fitting parameters—correlation coefficient (R²), residual sum of squares, and root mean square error (RMSE) shows that the Kostiakov model was more suitable than the Philip model. 【Conclusion】All the findings demonstrate that the process of soil water infiltration is greatly influenced by soil surface electric field. There are critical surface potentials controlling water infiltration. The findings provide a theoretical reference for development of new techniques to regulate water infiltration based on soil internal forces.