Hydrodynamic parameters should be identified firstly for predicting soil and water loss with specific issues and objectives. The laboratory simulation scouring experiments were conducted with different gravel contents, flow discharges and slopes based on the field investigation, which achieved the most suitable parameter for predicting soil and water loss on simulation landslide deposit slope in Wenchuan earthquake area, China. The results showed that the gravel content of 25% always was the threshold that controlled the flow shear stress (tau) and stream power (omega) increased or decreased under different flow discharges. The unit stream power (UP) and unit flow energy (E) both decreased when gravel contents increased. The ratio of Manning coefficient to flow depth (n/h) was higher in fine sediments with gravels than that without gravels. The flow discharge had the consistent effects on hydrodynamics which was ordered as 4<8<12 L min(-1). The tau was the most suitable parameter for predicting soil and water loss by considering the degree of reliability, even though the omega also had significant positive power function with soil and water loss. The n/h could describe the hydrodynamics and soil and water loss and be the alternative parameter for predicting soil and water loss. The results provide useful information for soil and water loss prediction in landslide deposits.