Flume experiments were conducted with the combinations of five flow rates (20, 30, 40, 50, and 60 L/min) to clarify the effects of hydraulic characteristics on yellow soil detachment capacity (D_c) under different bulk densities (1.06, 1.15, 1.18, and 1.21 g/cm³) in karst area, and establish the prediction model for D_c. The results showed that both flow rate and bulk density significantly affected D_c. When the bulk density was 1.06 g/cm³, D_c increased with the flow rate as a power function, while D_c increased with the flow rate as a linear function under other higher bulk density conditions. Under the same flow condition, D_c decreased with the increase of bulk density, and the reduction trend was more obvious under the higher flow condition. Power functions could be used to describe the relationships between Dc and shear stress (τ), stream power (ω), unit stream power (P), and unit energy (E), respectively, while τ showed the best predictability (R²=0.96). The erodibility values (K_τ, K_ω, K_P, and K_E) and critical values (τ_C,ω_C, P_C, and E_C) corresponding to hydraulic parameters all presented decreased trend with the increasing bulk density, and these erodibility values were negatively linearly correlated with bulk density. The results will provide theoretical basis for understanding the mechanism of soil erosion in karst area and establishing soil erosion process models.