Soil conservation service is an important regulating service that can prevent regional land degradation and reduce the risk of flooding. Focusing on the most influential soil erosion type, water erosion, this paper first clarifies the scientific concept of soil conservation service based on soil erosion, transport, and export processes. Soil conservation service is defined as the capacity of the ecosystem to prevent soil erosion and retain sediment. Then, an analysis of the assessment methods used to evaluate soil conservation service was undertaken. Based on the revised universal soil loss equation, soil retention (calculated as potential soil erosion (erosion without vegetation cover) minus actual soil erosion) was applied as an indicator of soil conservation. The effectiveness of soil erosion at the individual-plant scale depends on plant morphology. As the scale increases, land use gradually plays an increasing role in curbing soil erosion, and large basins are more closely related to fluvial erosion and storage processes. Considering the scale-dependency of the erosion processes, a multi-scale method is needed to assess soil conservation service. The models used to quantify soil conservation service mainly address soil detachment processes only, and do not simulate soil redistribution, by ignoring processes such as sediment deposition and transport. Additional studies of sediment deposition and transport are needed. Soil conservation service can be considered a link between biophysical reality (the ecological system) and human well-being (the socio-economic system). To fully understand the effects of soil conservation on human well-being, the supply and the demand of soil conservation services both need to be measured.