Abstract: Raindrop impact can increase solute transport process from soil into surface runoff. A laboratory flow cell and experimental procedures to study chemical transport from soil to runoff as a diffusion process were developed. Different vertical hydraulic gradients were imposed by setting the flow cell to free drainage condition (-5 cm), saturation condition and artesian seepage conditions (5 cm) under 30, 60 and 90 mm/h simulated rainfall and 2, 4 and 10 times simulated flow rate to rainfall. The experimental data clearly demonstrated that all of rainfall intensity, total flow rate, and water table can accelerate diffusion process. There is an interaction between diffusion and convection to increase chemical loss from soil into runoff under artesian seepage conditions. Chemical transport has a significant relationship to rainfall intensity, surface runoff flow rate and groundwater table.