Particle size is an important index used to evaluate the quality of flour, as it influences the properties of wheat flour and its products. In order to study the specific effect of particle size on flour quality, four commercial flours were classified into four particle size ranges (140~160 mesh, 160~180 mesh, 180~200 mesh, and 200 mesh and above) by sieving. The distributions of the four commercial flours across the different size ranges were studied, and a laser particle size analyzer was used to scan the particle size distribution of flour in each range. The gluten index and the contents of moisture, ash, damaged starch, crude protein, wet gluten, and dry gluten of all ranges of flour were measured, and the change in the composition and differences in the physicochemical indices of all ranges of flour were analyzed. The results showed that a small particle size led to a high content of damaged starch. The physicochemical properties of the flour samples in the ranges of 160~180 mesh (96~80 μm) and 180~200 mesh (80~75 μm) were significantly different from those in other ranges, and variance analysis showed significant differences in the damaged starch content, crude protein content, dry gluten content, wet gluten content, and gluten index among the flours with different particle sizes.