This study aimed to comprehensively examine the spatial and temporal variations in soil erosion within a watershed from 1986 to 2020. Specifically, it sought to quantify the intensity of soil erosion, pinpoint key sand-producing regions, and introduce the concept of sediment connectivity to explore the spatial and temporal changes in soil erosion and sediment transport capacity, as well as their responses to soil and water conservation measures. Based on the measured sediment transport data of the Luoyugou watershed, the study simulated the soil erosion and sediment transport capacity and their spatial-temporal distribution patterns from 1986 to 2020. The simulation results were then integrated into the sediment connectivity model to conduct a sediment connectivity assessment that accounted for the erosion intensity. (1) In the mid-1990s, the watershed launched the slope-to-terrace project. As a result, the proportion of terraced areas in the basin soared from 11.58% in 1986 to 55.89% in 2020. Moreover, with the implementation of the project of returning farmland to forest and grassland at the end of the 1990s, the vegetation cover increased by 41.33%. Under the influence of these soil and water conservation measures, the sediment transport modulus decreased significantly. It dropped from 9542.5 t/km² during 1986-1989 to 1949.35 t/km² during 2010-2020, representing a remarkable 79.57% reduction. (2) The WaTEM/SEDEM model was employed to assess soil erosion in the watershed. Under the combined influence of terrace construction and the increase in vegetation cover, the percentage of the watershed area experiencing moderate or higher soil erosion decreased substantially, from 83.83% to 26.33%. (3) The Luoyugou watershed exhibited distinct spatial differentiation in sediment connectivity. Areas with steep topography, adjacent to the main river channel, and their neighboring regions displayed high sediment connectivity. In contrast, forested areas and terraced fields werecharacterized by low sediment connectivity values. The implementation of large-scale slope-to-terrace conversion projects and the return of farmland to forest and grassland led to a significant decreasing trend in both erosion intensity and sediment connectivity in the watershed. By using the WaTEM/SEDEM model and the sediment connectivity assessment model, this study systematically elucidated the spatial and temporal changes in erosion and sediment connectivity in the small watersheds of the Loess Plateau and their responses to soil and water conservation efforts. These findings offered a scientific foundation for understanding the spatial transport processes of small watersheds on the Loess Plateau under current ecological policies and for implementing high-quality management of soil and water erosion.