The ecosystem services flow establishes a spatial-temporal connection between the supply and beneficiary sides, playing a crucial role in the formation, transportation, transformation, and maintenance of ecosystem services. Spatial quantitative research on this topic is beneficial in systematically revealing the transfer processes of ecosystem services. However, current static assessments of ecosystem services neglect the ecosystem services flow caused by the spatial unbalance between supply areas and benefit areas, which reducing the guiding role of ecosystem services in ecological protection and construction efforts. We used surface process modeling and GIS spatial analysis technology to quantitatively predict the spatial flow of soil conservation services in the Shiyang River Basin (SRB). We supplied spatial descriptions, mapped the flow path and direction, and examined the features of the temporal and spatial changes. According to the results, the SRB's soil conservation service flow showed a geographical distribution between 2005 and 2020 that was higher in the southern region and lower in the northern region. The SRB's flow exhibited a cyclical rising pattern, with a steady rise in the top section and a gradual decrease in the middle and lower sections. The overall flow of soil conservation services is between 114.27 and 206.53 million tons; with time, the tendency fluctuates between decreasing and increasing, eventually convergent from southeast to northwest spatially. In the lowest parts of the basin, soil conservation service flows are progressively decreasing and increasing more slowly upstream. The basin features short soil and water conservation service flow pathways, upstream and central reaches beneficiary areas, and supply areas that are cross-distributed with beneficiary areas. Grasslands are the main source of service flows for soil and water conservation in the SRB. This study contributes to the precise spatial assessment of actual ecosystem services, which is of significant importance for the implementation of ecological management policies such as ecological restoration and ecological compensation.