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The dust emission models to date cannot describe the relation between the transport rate of different sized grains and their grain size composition in soil surface, so Aeolian grain transport on a soil-like bed composed of fine sand and silt powder was measured in a wind tunnel. Six types of soil-like beds with different silt fractions have been tested in this experiment. The mass flux profiles of silt dust and sand grains are much different due to their different motion modes. Analysis of the vertical distribution of the powder and sand grains reveals that for a given soil bed, the ratio of the horizontal dust flux to the horizontal sand flux is directly proportional to their mass ratio in the bed. The dust flux is closely linked to the sand flux by the bombardment mechanism. For a given wind velocity and grain size of the bed, the slopes of the vertical mass flux profiles of sand grains larger than 100 μm are nearly equal in a log-linear plot and the ratio between the fraction of transport rate of each size group to the whole transport rate and the mass fraction of each size group in the bed is a constant only dependent on grain size. With this law, the transport rate of dust and different sized grains can be related with the grain size composition in the soil surface.wind erosion, dust, transport rate, grain size Grain erosion on the soil surface under a strong wind has a close relation with humanity. This type of motion induces the loss of nutrition and the coarsening of soil surface. Since the 1930s, many researches have been carried out to study the physical mechanism of grain movement in the wind erosion on the soil surface. Some revealed that soil grains took many different spatial performances in the erosion process. Fryrear et al.'s [1] field experiment shows that in the wind erosion, the grains in saltation mainly move below the height of 0.25 m and the mass flux profile within this height is an exponential function, whereas the grains flying above 0.25 m are mainly in suspension and the mass flux profile is nearly a power function. By observing in field, Vories et al. [2] suggested a power function for the suspension profile above 0.5 m. According to the difference of grain motion mode, the soil grains can be classified into big grains in saltation and dust grains in suspension. Due to the long flying distance of dust grain, its large influential scope and great harm to the environment, the researches on the dust emission law and its mechanism are very important.To explore the movement mechanism of dust grains, many wind tunnel experiments were carried out. Shao et al. [3] indicated that the bombardment of large grains impacting onto a bed surface was the main mechanism to release dust. Many experiments showed that the dust flux was directly proportional to the flux of grains in saltation in soil erosion and proved Shao et al.'s theory correct. Based on this theory, some models have been developed to calculate the dust emission flux. So far, only two models of dust flux involve explicit physical param...