The solid-gas two-phase flow model is combined with the granular material model to simulate the detailed mechanics of sediment transport in wind-blown sand layer. The physical characteristics of the wind-blown sand layer is investigated from the viewpoint of computational mechanics of sediment transport by taking into account the sediment-flow interaction and the interparticle collision. Changes in the windvelocity profile and the Reynolds stress profile due to the load of sediment are calculated. The velocity and the existing probability density of moving particles, and the distribution of colliding frequency of particles are estimated to consider the physical structure of the wind-blown sand layer.