The abrupt changes of soil properties after shallow landslides were found to greatly increase the soil erosion on loess slopes in field and laboratory experiments in Loess Plateau, but which properties play the dominant role under various conditions is still unclear. To address this issue, a simplified runoff and soil erosion model was applied to quantitatively identify the contribution of four changed properties at the landslide scar on soil erosion aggravation after a shallow landslide. The slope angle, soil, and the length and location of the landslide scar were further analysed in detail to determine if the dominant roles vary with these parameters. The results show the model can accurately simulate the sediment yields before and after shallow landslides. After shallow landslides, the increasing rainfall excess rate and soil erodibility play dominant roles in soil erosion aggravation, which cause 4.95-90.75 and 3.08-17.92 times larger sediment yields, respectively, than those before shallow landslides. Moreover, the effects of increasing rainfall excess rate and soil erodibility can complement and reinforce each other in the soil erosion aggravation following a shallow landslide. A sensitivity analysis shows that the dominant factors remain unchanged, even though the impacts of changed soil properties on soil erosion aggravation can vary substantially for different slope angles and shallow landslide characteristics. In addition, using a temporally varying soil erodibility in the landslide path can account for the impact of remnant loose soil over there, and the simulation agrees much better with the observations. These results are expected to deepen our understanding of how shallow landslides aggravate the following soil erosion and formulate an optimal strategy to control the combined gravity-hydraulic erosion in the Loess Plateau.