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Field experiments on two isolated transverse dunes with different scales in the Taklimakan Sand Sea show that particle size and slope control the threshold shear velocity and sand flows on the stoss of the dunes. The decreased threshold shear velocity and the unsaturated sand flows are the main reasons why sands are not deposited at the toe of the dunes. The particle size controls sand flux through its influence on the aerodynamic roughness elements and threshold shear velocities. The sand flux is different for dune surfaces with different particle size distributions. Under the control of the medium to low stress of the drifting-sand winds, the results of the field experiments and particle size analysis showed that sand transport had little influence on the particle size distributions. The mean particle size being transported on the stoss is lower than that on the dune surface, It is difficult to determine whether or not the wind is fully saturated with sands when sand flux calculation is mainly dependent on the shear velocity and the mean particle size. The sands within some range of the particle size are transported and developed into simple transverse dunes, and then the interdune surface is coarsened and alternated with the draas in the Taklimakan Sand Sea. Copyright (C) 2002 John Wiley Sons, Ltd.