Biological soil crusts (BSC), commonly distributed as ground cover in arid and semi-arid regions, are recognized for the significant role in regulating runoff yield processes. However, the hydrodynamic properties of overland flow over BSC surface remain poorly understood. A comprehensive analysis of the velocity distribution and turbulent characteristics of overland flow on the BSC slope was conducted and detailed through Particle Image Velocimetry (PIV). The results showed that PIV is an effective method for observing the velocity distribution of overland flow over BSC surface, with flow velocities categorized into three regions: the rough sublayer, logarithmic layer, and outer layer. The velocity correction coefficients (a) for overland flow in both the control (CK) and BSC treatments exhibited logarithmic increases with Reynolds number (Re). In comparison to the flow characteristics of CK, the overland flow of BSC treatment was observed to enhance the intensity of near-bed turbulence while preserving the vertical distribution of turbulent intensity. The hydraulic impacts of overland flow on the BSC slope were found to be significantly influenced by the degree of submergence. Under high submergence conditions of BSC, Reynolds shear stress was identified as the dominant component of bed shear stress. This investigation aimed to elucidate the regulatory mechanisms of BSC on runoff processes and provides essential information for the parameterization of erosion models. (c) 2025 International Research and Training Center on Erosion and Sedimentation and China Water and Power Press. Publishing services by Elsevier B.V. on behalf of KeAi Communications Co. Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).