The present study was carried out to investigate the starch granule size distribution in grains of wheat. This information will help to elucidate the characterization of starch granule in the superior and inferior gains in winter wheat. The volume%, surface area% and number% distribution of starch granules were investigated in three winter wheat cultivars (Shannong12, Lumai21 and Jinan17), differing in starch content, in Tai'an experimental location in Shandong Province during the 2004-2006 growing season. The results showed that both superior and inferior grains contained three types of starch granules: smaller C-type granules with diameters ＜2.0 μm, medium B-type granules with diameters 2.0-9.8 μm and large A-type granules with diameters ＞9.8 μm at maturity. Both volume% distribution and surface area% distribution of starch granules in superior grains showed the typical three populations, and those in inferior grains exhibited the two peak curve. The volume% and surface area% of starch granules with the ranges of ＜2.0 μm in superior grains were 7.25%-9.31% and 34.88%-41.51%, respectively, and those in inferior grains were 5.33%-6.40% and 26.31%-33.54%. Significant differences were seen among the superior and inferior grains for number% of starch granules with the ranges of ＜0.6 μm and 0.6-2.0 μm. The number% in inferior grains was 25.72%-37.42% and 52.77%-58.48%, and that in superior grains was 1.86%-6.13% and 83.77%-87.77%, respectively. Compared with irrigation, the volume% and surface area% of B, C-type starch granules were significantly increased, and those of A-type were evidently decreased. The number% of starch granules with the ranges of ＜0.6 μm in inferior grains under rainfed condition was significantly increased, and that in superior grains had no evident difference. The volume percentage and surface area percentage of C granules and protein content in superior grains were higher than that in inferior grains, but those of A, B granules in superior grains were lower than that in inferior grains. Compared with irrigated condition, rainfed condition can increase the volume percentage and surface area percentage of B, C granules and protein content in superior and inferior grains.