Mechanical pulverization was generally used to fractionate starch granules, but this method produced broken starch granules, thus resulting in the difficulties in finding the relationship between particle size of starch granule and hydrolysis efficiency by enzymes. Therefore, a sedimentation method based on stokes law was developed to produce unbroken starch granules with different particle sizes. The results showed that four sizes of starch granules were obtained and their average equivalent particle diameters were 17.39, 25.81, 38.77, and 56.53 μm, respectively. Furthermore, smaller starch granules possessed large specific surface and exhibited higher hydrolysis rate. A negative correlation was observed between granule size and digestion rate (K). These findings suggest that smaller starch granules could be used as materials for porous starch and larger starch granules could be applied to prepare resistant starch.