【Objective】 Revegetation of the Loess Plateau, especially since the implementation of large-scaled “Grain for Green” projects, has brought about great changes in land surface coverage and underlying surface (or subsoil layer) of the plateau and altered significantly physical properties (soil structure, porosity, etc.) of the soil. Such dynamic changes in the environment may generate very important impacts on hydrological processes, hydrological fluxes, water balance, and ecosystems at a watershed scale. In recent years, rainfall-infiltration-runoff processes and their mechanisms as affected by global warming have become a hot topic in the field of hydrology. Therefore, the study to explore water storage capacity of and rainwater infiltration processes in soil profile under severe rainstorm may help expose processes and mechanisms of soil hydrology, soil erosion and surface runoff, and hence is of great scientific value to elucidation of processes of runoff generation and convergence and their influencing mechanisms. 【Method】In this paper, a real-time dynamic soil water monitoring system was used to monitor soil moisture layer by layer at 10 cm intervals in 2 m soil profiles in a tract of grassland in a hilly and gully loess region during the “7•26” severe rainstorm event in northern Shaanxi Province. Data of the rainfall event was obtained from the meteorological station of the region. Both rainfall data and soil moisture data were extracted at 1-hour intervals. Based on analysis of the rainfall and soil moisture data, dynamic changes, distribution characteristics and soil water storage capacity of the soil water in the profiles during the severe rainstorm event were acquired. And with the aid of the Horton infiltration model, movement and infiltration processes of the soil moisture wetting front in the grassland profiles were simulated. 【Result】Results show: (1) the response of soil moisture in the profile to the rainfall varied with process of the rainfall and depth of the soil layer. The soil profile could be divided into three layers, i.e. soil moisture quick-changing layer (0~ 60 cm), soil moisture active layer (70~ 140 cm) and soil moisture stable layer (150~ 200 cm), with soil water varying in the range of 15.49~ 16.72 mm, 2.01~13.27 mm and 0.22~ 0.44 mm, respectively; (2) The 0~140 cm soil layer is critical to the soil hydrological process in the profile, with average water storage being 26.49% higher than that of the 150~ 200 cm soil layer. The soil water storage of that layer could reach as high as 225.99 mm, 1.37 times its initial water storage capacity (95.37 mm). Thereinto, the 0~100 cm soil layer is the one with available soil water closely related to its grass cover; (3) In this area, soil infiltration depends on physical properties of the soil. Soil steady infiltration rate decreases with increasing soil bulk density, and the decrease declines in magnitude with risng bulk density, too；and (4) Rainwater infiltration rate on grassland hillslopes (P< 0.01) shows a decreasing trend with the time going. The attenuation is high in rate in the initial period and turns low. The infiltration rate varies exponentially with time. Cumulative infiltration (R²= 0.99, P< 0.01) shows a logarithmic relationship with wetting front movement process (R²= 0.99, P< 0.01) along the time series. The Horton infiltration model is suitable for simulation of the infiltration process (R²= 0.97, P< 0.01) as affected by severe rainstorm. 【Conclusion】During the severe rainstorm event, the mechanism of runoff generation is still dominated by infiltration excess runoff on hillslopes of the region. The increase in infiltration can reduce runoff volume and delay runoff generation to a certain extent, which has a significant impact on the mechanism of runoff generation.