To reveal the effects of soil surface roughness on sheet erosion, the changes of soil surface roughness on purple soils were studied during the whole growing stages of maize based on field artificial rainfall experiments, and the effects of soil surface roughness on runoff and sediment yield of sheet erosion process were analyzed. The results showed the soil surface roughness presented an increasing-first-and-then-decreasing trend with the advance of maize growing period under the rainfall intensity of 1.0 mm/min, and the maximum of increasing range appeared in maize seedling stage and the maximum of decreasing range appeared in mature stage. Under the rainfall intensity of 1.5 and 2.0 mm/min, the soil surface roughness presented a decreasing-first-and-then-increasing trend with the advance of maize growing period, and the changing range of soil surface roughness was the?greatest at the stage of maize seedling - jointing. Under the rainfall intensity of 1.0 mm/min, the changes of soil surface roughness presented a decreasing-first-and-then-increasing -and -decreasing trend, and these changeswere consistent with the changes of surface runoff under the rainfall intensity of 1.0 mm/min. At the stages of maize seedling-jointing and jointing-tasseling, the changes of soil surface roughness were consistent with the changes of surface runoff under the rainfall intensity of 1.5 and 2.0 mm/min, but inconsistent with the changes of surface runoff at the stage of maize tasseling- mature. At the stages of maize seedling and jointing, the changes of soil surface roughness showed the consistency with the changes of sediment yield intensity, however, they presented the opposite?changes in soil surface roughness and sediment yield intensity at the stages of maize tasseling and mature. In maize jointing stage, there was a very?significant negative relationship between the changing range of soil surface roughness and runoff amount, but a positive relationship between both in maize tasseling stage. In maize seedling, jointing and mature stage, there were the significant or very?significant positive relationships between the changed range of soil surface roughness and sediment yield amount, however, a very significant negative relationship in maize tasseling stage. These results would provide theory basis for posing the sheet erosion nature of soil surface roughness, and also serve for harnessing soil and water loss of the slope farmland.