The flow-sedimentation coupled model is a crucial tool for quantitatively describing the relationship and the law of flow and sedimentation. Studies on flow-sedimentation model at home and abroad are almost empirical statistical models of a typical basin or physics-based model based on considerable description of the watershed at this stage, which greatly limits its usage and simulation accuracy. A conceptual flow-sedimentation coupled simulation model for basins, which combines the conceptual hydrological model with the sediment model, is presented with physical structures and parameters in this paper. Its clear physical concept, high simulation precision and strong practicability make it easy to study the basic law of sediment. We put forward the concept of hydraulic erosion capacity and soil erosion resistance capacity to estimate the sediment yields on the slopes and use logarithmic curve to approximately describe the spatial variability of watershed soil erosion resistance capacity. The calculus formula for sediment yield in gully and sediment concentration is respectively established based on the suspended sediment formula of the Bagnold's River channel and by referring to the similarity of flow. The proposed model is tested in four watersheds of different scales in the Dali River Basin and the results indicate that the model can provide a good simulation of runoff and sediment generation as well as transportation processes at both watershed scale and inter-annual time scale in the middle reaches of the Yellow River, and thus further confirm that the model is reasonable in structure, parameters and calculation methods. The model can be used to quantitatively analyze the benefits of flow and sediment reduction and how their relationship changed due to various water conservation measures implemented in the basin, and can be further analyzed and studied for its popularization and application.