【Objective】The Freezing-thawing action refers to daily, annual and secular climate change that might lead to freezing and thawing of the earth’s surface in a certain climatic region. When the soil is frozen, soil water is frozen, too, thus expanding in volume and the expansion destroys the connectivity between soil particles, and hence change particle size distribution of soil particles. And during the thawing period, owing to the existence of both thawed soil layer and frozen soil layer at the same time, the soil differs sharply in erodibility from those completely frozen or thawed. However, studies focused mainly on changes in soil erodibility before and after freezing and thawing and gave little attention to studies on erodibility of frozen soils. Under the joint actions of hydraulic erosion and freezing-thawing erosion, the slope varies sharply in soil erosion and sediment particle size fractionation from those under the single action of hydraulic erosion, however, it is still unclear how soil erosion and sediment particle size fractionation varies under the joint actions.【Method】 Therefore, an indoor experiment was carried out using simulated rainfall to explore effects of freezing/thawing on water erosion during the thawing period on slopes of loess, processes of soil erosion on frozen and thawed slope and particle size fractionation of sediment. 【Result】Results show that affected by rain, runoff initiated 173 seconds earlier on the thawed slope than on the frozen one, while runoff rate and sediment yield was 9% and 105% higher, respectively. In terms of MWD of sediment particles generated during the processes of soil erosion on the two slopes, an order was observed as splash particles > scouring particles, but MWDs of the two types of particles were both significantly higher on frozen soil slopes than on thawed soil slopes (p < 0.05). During the erosion process with the rainfall going on, the contents of clay and fine silt increased first and then decreased, but the contents of coarse silt and sand did reversely, on the thawed slopes, while the sediment got dominated with coarse particles. However, particle size fractionation of the sediment on frozen slopes did not vary much with the time going on.【Conclusion】On frozen slopes, the existence of an aquiclude aggravates the soil erosion, but during the hydraulic erosion process, the erosion was low in selectivity of sediment in particle size relative to that on thawed slope. This paper is expected to provide some valuable reference for better understanding the mechanism of soil erosion.