Soil erodibility is the intrinsic factor which has effect on water erosion on slope and is related to soil texture,soil organic matter,and other soil properties. Sediment particle is analyzed by using plot data from rainfall simulation experiments. Results show that (1) during rainfall,particle composition of sediment changes with time. Sand content increases,silt content keeps constant,and clay content decreases. (2) Rainfall intensity is the important factor to the particle composition of sediment. With rain intensity increasing,sand content increases and slit and clay contents are reduced. (3) The effect of slope gradient on sediment is complicated. When slope becomes steeper,sand content increases first and then decreases,whereas silt and clay contents decrease first and then increase. When slope gradient is 20°,sand content reaches the maximum and slit and clay contents,the minimum.