Rainfall characteristics and slope gradients are important factors that affect soil infiltration process, and their effects on soil infiltration characteristics may be different during the process of vegetation restoration. To discuss the effects of rainfall process parameters (rainfall, mean rainfall intensity, rainfall duration and I₃₀), inclination of slopes and vegetation coverage on the infiltration characteristics, six runoff plots of two-years abandoned grassland with the slope gradients of 5°, 10°, 15°, 20°, 25°, and 30° were selected in the hilly region of the Loess Plateau, and their soil infiltration characteristics were observed in the peak period of vegetation growth (July to September) under natural rainfall (34 rainfall event and 11 rainfall-generated runoff). The results indicated that:(1) For the 11 runoff-producing rainfall under different slope gradients, the variations of soil infiltration amount was ranged from 6.58 to 70.91 mm, the infiltration supplement coefficient was ranged from 0.83 to 1.00, and the infiltration rate was ranged from 0.22 to 19.35 mm/h; (2) The amount of soil infiltration increased linearly with rainfall capacity (R²=0.99, p<0.01) and the infiltration supplement coefficient decreased exponentially with I₃₀ (R²=0.91, p<0.01). While for the average infiltration rate, it was increased linearly with rainfall intensity (R²=0.71, p<0.01) and decreased exponentially with rainfall duration (R²=0.99, p<0.05); (3) The increase in slope gradient extended the runoff displacement, resulting in the exponential increase in the infiltration volume, the infiltration supplement coefficient, and the average infiltration rate. However, when the slope gradient exceeded 25°, the component of runoff potential energy increased along the slope direction, the runoff velocity speeds up, and the above-mentioned infiltration characteristic parameters decrease slightly. (4) The amount of rainfall showed a downward trend during vegetation growth cycle, which to some largely extent manipulated the influence of vegetation on the infiltration characteristics, so the infiltration amount decreased significantly with the vegetation coverage. In general, rainfall characteristics and slope gradients are the main factors affecting soil infiltration, and soil infiltration characteristic parameters can be expressed as the comprehensive power function equation of rainfall process parameters and slope gradients. The effect of vegetation coverage on soil infiltration characteristics was weakened as the infiltration supplement coefficient was high. This study is of great significance for the research of rainfall-runoff regulation mechanism and eco-hydrological process at slope scale.