In this research the transformation of rainfall into runoff was simulated using two dimensional SV equations in the Kamanaj watershed, a subwatershed of Ajichay river, located in East Azarbaijan Province, Iran. Rainfall-runoff was simulated based on a diffusive model by considering momentary infiltration rate for temporal and spatial analysis. SV equations were solved using explicit method of finite difference numerical technique as the initial and boundary conditions were defined. For this purpose, the watershed area was divided into a grid size of 250m x250m by the tools of GIS leading to prepare digital elevation map. Kostiokov infiltration, as the best fitted model, was selected to measure infiltration data and applied in SV equations. Three hydrographs were used to verify the model. Comparison of the simulated and observed hydrographs verificated the capability of model in simulating the rainfall-runoff. The presented model can be used for determination of runoff from momentary rainfall with consideration of temporal and spatial variation of infiltration over the watersheds.This model can also be used to forcast the peak discharge and time to peak in watershed outlet.