Large-scale roughness element plays an important role in soil erosion control, but few studies have been performed to quantify the effects of large-scale roughness element on hydraulics of overland flow. Laboratory flume experiments were conducted to investigate the potential effects of large-scale roughness element on flow velocity, water depth, Froude number, and hydraulic resistance of overland flow. The plastic hemispherical were glued onto the flume bed to simulate the large-scale roughness element, and a sand cloth bed was used as control. The flow discharges varied from 2.81 L/min to 84.43 L/min and the slope gradients ranged from 2° to 10°. Results showed that:(1) The mean flow velocity, mean water depth and Froude number had power function relationships with the flow discharges and slope gradients. However, the resistance coefficient decreased as Reynolds number increased. (2) The variation trend of water depth around the large-scale roughness element was water depth in front of the large-scale roughness element (h₁)>water depth on both sides of the large-scale roughness element (h₂)>water depth behind the large-scale roughness element (h₃). At a smaller slope gradient, h₁-h₃ increased first and then became stable with the increasing flow discharges. At a larger slope gradient, h₁-h₃ increased first and then decreased with the increasing flow discharges. (3) Compared with the sand cloth bed surface, the large-scale roughness element had a function of reducing flow velocity, increasing resistance, and changing flow regime. (4) The total resistance on large-scale roughness element was partitioned into grain resistance and form resistance, and form resistance accounted for 29%~77% of the total resistance. In a word, the large-scale roughness element cloud retards the flow, reduce soil erosion and have obvious effect on soil and water conservation.