Based on the Boltzmann transport equation, a theoretical model for the particle concentration distribution was developed in the aeolian sand transport to account for the inter-particle collision effects near the sand bed surface. In order to assess the inter-particle collision effects on sand transport characteristics near the sand bed surface, a set of experiments were performed in a large-scale wind tunnel with a dimension of 12,000 mm x 400 mm x 600 mm (L x W x H). Two types of sand samples were prepared by screening. The free-stream wind velocity in the wind tunnel was measured by HWA (Hot Wire Anemometer). The particle velocity, concentration, and Reynolds stress were obtained by PDPA (Phase Doppler Particle Analyzer). Experimental results showed that particle concentration emerged a turning point at about 2 cm from the sand-bed surface. They agreed with the numerical simulation results very well. The collision rate of particles also emerged a turning point, and the location of the turning point was approximately consistent with that of the measured concentration and the Reynolds stress. Consequently, the inter-particle collision close to the sand-bed surface, which was the main factor that altered the characteristics of particle transport, could not be neglected. (c) 2012 Elsevier Ltd. All rights reserved.