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We investigated ecological processes that control surface water runoff and erosion in typical steppe of Inner Mongolia typical by measuring runoff in the field,simulated runoff in field,and simulated runoff in the laboratory under different conditions.We present several key findings.First,vegetation degradation is the primary factor causing fluctuations in surface runoff.A significant positive correlation was found between surface runoff and level of degradation.Both the surface runoff coefficient and runoff discharge increased with increasing levels of vegetation degradation.Second,plant height and plant density of the vegetation canopy also was a primary factor causing fluctuations in surface runoff.The surface runoff coefficient and the surface runoff discharge decreased gradually with increases in plant height anddensity.However,the influence of plant height was greater than plant density on surface runoff under certain conditions.Third,litter played an important role controlling surface runoff mainly by a direct interception effect and an indirect barrier effect.The influence of litter was greater than the influence of vegetation on surface runoff under certain condition.