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The situ test in a grass field was conducted in three kinds of vegetation cover grass at three wind speeds, then the velocity profile and sediment discharge were obtained for different vegetation coverage of grassland by using mobile wind erosion wind tunnel device. The results showed that grass wind profile was exponent in generally and increased rapidly with the increase of height of surface elevation. There was a good fitting results for sediment discharge and height by using exponential function in the height of 0~70 cm for different vegetation coverage grasses, and the sediment discharge was mainly concentrated under the height of 30 cm of surface elevation. The barrier effect of near-surface wind speed was similar between 55% and 80% vegetation coverage of grassland under the height of 10 cm. The sediment discharge curve was very close between 55% and 80% grassland vegetation coverage, but the former was far from the sediment discharge curve of degraded grassland in 30% grassland vegetation coverage. Therefore, the minimum vegetation coverage was about 50% for preventing wind erosion effectively in the northern of Yinshan mountain. 