[Background] Rainfall runoff is the major dynamic source for hill-slope erosion, runoff velocity is one of the important parameters in soil erosion model. The accurate measurement of shallow water flow velocity is critical in hydrological process. Lei et al. proposed an electrolyte pulse method for measuring the velocity by fitting the solute transport process with time using the least square method and improved the system with a Normal Model and a Sine Model. This laboratory experiments were conducted to determine the relationship between electrolyte peak velocity and water flow peak velocity during the electrolyte transport process and verify the new 程computational method. [Methods] The experimental devices include a flume, 4 m long and 15 cm wide, a solute injector, a data logger for control and data acquisition and a computer with specially designed software for data measurement and storage. The experiments involved three flow rates (12, 24 and 48 L/ min) and three slope gradients (4°, 8°and12°). Five sensors were used to measure the electrolyte transport processes at 0.3 m, 0.6 m, 0.9 m,1.2 m, and 1.5 m from the location where the salt solute was injected into the water flow. During each experiment, five complete curves of electrolyte changes with time were recorded, which can be used to calculate electrolyte peak velocity with the distance from the injection to the measuring sensor and the time used for the peak of the electrolyte to travel through the distance. The leading edge velocities were measured by floating objects method and mean velocities by volumetric method. [ Results ] The electrolyte peak velocity was between 0.15 to 0.54 m/ s, increased with distance and tended to stable, and the flow rates caused greater effect on electrolyte peak velocity than slope gradient under different conditions. The steady electrolyte peak velocity, regarded as the water flow peak velocity, were computed through fitting the electrolyte peak velocity at different distances from the salt solution injector with exponential function, ranging from 0.241 to 0.568 m/ s. The exponential function fitted the electrolyte peak velocities very well for all the experimental conditions. The flow rate had greater effect on flow peak velocity growth rate than that of slope gradient. The water flow peak velocity were 1.007 times of mean velocity, 0.774 times of leading edge velocity, and mean velocity was 0.776 times of leading edge velocity. [ Conclusions] The flow peak velocity agreed well with leading edge velocity and mean velocity. These demonstrated that the new computational method for measuring shallow water flow velocity was reasonable and valid. The results provide a new method for computing the mean velocity of sheet flow and relevant data for the dynamic process of sheet flow, which will be useful for the investigation of soil erosion.