SWAT was applied to Xitiaoxi catchment for surface runoff simulation.The model was calibrated and verified using observed data of stream flow at Fanjiacun gauging station in 1988—2001.An efficiency of greater than 0.88 was achieved in quantifying the model's fitness with the observation.A deviation of less than 4% was found in comparison of the predicted volume of stream flow with the observed one.Rainfall-runoff relationship and water balance were analyzed on the basis of the modeling results.The outcomes indicate that rainfall-runoff relationship in Xitiaoxi catchment has no significant alteration in the simulation period.The annual rainfall precipitation varies significantly.The monthly runoff and peak storm flow in wet seasons have a tendency of slow increase

which is affected mainly by rainfall.The water balance analysis indicates that the percentages of stream flow

evapotranspiration

and groundwater recharge over the amount of rainfall are 54.1%

45.8% and 17.3%

respectively.