Abstract: Soil erosion by wind is a major cause of farmland degradation in arid and semiarid area of north China. In this paper, a movable wind tunnel was employed to carry out the field tests both on conservation tillage field and conventional field ploughed in fall. The characteristics of drifting sand flux for conservation tillage field and conventional tillage field, and the influencing mechanism of conservation tillage on soil erosion by wind were analyzed. It provides a theoretical basis on preventing farmland wind erosion. The results show that the wind speed can be rapidly reduced on conservation tillage field due to the standing residual stubble by contrast with the conventional tillage field, especially the logarithm relationship between wind velocity variation and residual stubble height was changed. Also the configuration of drifting sand flux was changed, which was mainly occurred at height of 180-400 mm, and accounted for 67.94%-69.28% of total sediment discharge. The maximum sediment discharge rate was emerged at height of 240 mm above the soil surface, and the shapes of drifting sand flux structure like an elephant nose, so that it was named “elephant nose effect”. The total sediment discharge rate of the drifting sand flux was apparently lower than that on compared conventional farmland, indicating that the conservation tillage is an effective approach of preventing field from wind erosion and desertification.