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To reveal the effects of biological soil crusts (BSCs) on soil particle size characteristics in Mu Us Sandland, soil samples under algae, lichens, and mosses crusts as well as the uncovered sandland were selected in Yanchi research station. Soil particle size distributions were identified by using laser diffraction technique. Particle size parameters were subsequently calculated including average particle size, standard deviation, skewness, kurtosis and fractal dimension. The results indicate that the majority soil particle size is occupied by sand particles approximately accounting for 80%~95% of the total volume; accordingly clay and silt particles contents are much less; soil particle size distributions in different sites are comparatively centralized that resulted in poor sorting, very positive skewness as well as sharp or very sharp kurtosis; the fractal dimension of soil increases progressively across the successional stages of BSCs in range of 2.15~ 2.30. In short, as affected by BSCs, clay and silt particles continue to increase leading to constantly particle distribution optimization, and soil particle size distribution inclines to uniform and symmetric pattern. Therefore, BSCs are beneficial to soil improvement and development, but rather slowly.