The effects of soil and water conservation on surface runoff process in small watersheds of the Qinba mountainous region are analyzed by the parallel observation in two comparable watersheds.Comprehensive control of soil and water loss in the region can result in an increase in flood peak time by 30～60 min,and a decrease in runoff modulus by 25%～71%.Its effects are different for different rainfall intensities and rainfall amounts,and it decreases flood peak value by 14%～90%.It can also effectively retain precipitation in rainy season,and increase runoff in dry season.