Abstract:In order to reveal the erosion variation law of the Quaternary red clay slope under different rainfall intensities and slope gradients in mulching conditions, three representative rainfall intensities (1.0, 1.5, 2.0 mm/min) and three typical slope gradients (10°, 15°, 20°) in red soil hilly area southern China were selected. The characteristics of runoff, sediment yield and infiltration were analyzed by artificial simulation rainfall experiment. Moreover, taking 15° as an example to calculate the effect of reducing the flow and sediment on the slope. The results showed that:(1) The time producing runoff was advanced with the increase of rainfall intensities and slope gradients. The mulching had obvious hysteresis effect on the runoff yield time. However, the increase of rainfall intensities would weaken the effect of mulching on delaying runoff production. The runoff rate increased in the early stage and become stable in the later stage. (2) At the same slope gradient, the rainfall intensities increased from 1.0 mm/min to 2.0 mm/min, and the total amount of sediment yield increased by 1.89~2.96 times. When the rainfall intensity was constant, and the slope gradients increased from 10° to 20°, the total amount of sediment yield increased by 1.91~3.45 times. (3) The initial infiltration rate and the cumulative infiltration of soil decreased with the increase of slope gradients. While the increase of rainfall intensities increased the initial infiltration rates of mulched slope and reduce the cumulative infiltration. (4) Under the condition of 15°, the runoff and sediment volumes of the mulched slope decreased by 50.26% and 95.31% respectively, and the soil and water conservation effect of pine needle mulching was significant. In addition, the sand reduction effect was greater than the flow reduction effect. (5) The influence of slope gradients on the cumulative runoff and sediment yield of mulched slope was greater than that of rainfall intensities. There was a power function relationship(R2>0.97) between the cumulative runoff and sediment yield under different rainfall intensities and slope gradients. These results could provide reference for soil erosion control and ecological restoration in the red soil hilly region of southern China.