An improved particle counting method (denoted as M-count method) is proposed to calculate the particle volume concentration in aeolian sand transport in a wind tunnel. In the present M-count method, the thickness of the laser sheet of PIV (particle image velocimetry) system and the variation of particle diameter with height are considered. The laser sheet thickness is determined by an optical method, in which a full width at half maximum (FWHM) is used to express the width of laser sheet on the image. The mean particle diameter calculated by the pixel areas from Ply images at different height layer is also modified. The results show that the present M-count method is an available method for obtaining the particle volume fraction and also verified by the M-flux method in which the particle volume fraction is deduced from the sand mass flux and the mean horizontal particle velocity. The present M-count method is also helpful to study particle concentration in aeolian sand transport. (C) 2015 Elsevier B.V. All rights reserved.