The paper studied the change characteristics and regularity each surface roughness in the process of rainfall from microcosmic.Taking slope surface soil in yangling as the test soil,it used the artificial simulation rainfall and GIS technology and laser scanning measuring method,indoor experiment and computer simulation to study the variation characteristics of surface roughness when slope is 10 and 5 degree respectively, rain intensity is 60 mm/h under the measures of artificial hoeing and carry out hydrological analysis.The results show that the change of surface roughness at splash erosion phase is the most obvious and increases with the increase of slope; the change of topographic index is the most obvious in the presence of groove, the remaining phase is relatively stable; shape factor in splash erosion stage attains peak, then gradually decreases.After rill appears,the value is stable at relative low.The results enrich the theory of slope runoff can provide guide for agricultural production practice in the study area.