To investigate the effect of source-sink regulation on the distribution of starch granule size, two typical wheat (Triticum aestivum L.) cultivars, Shannong8355 (large-spike type) and Jinan17 (multi-spike type) were planted under both irrigated and rainfed conditions at the Tai′an Experimental Farm of Shandong Agricultural University in 2006-2007 growth season. Results indicated that the percentages of volume and surface area of A-type starch granules in mature grain were obviously higher than those in mid-filling stage in both cultivars. Under irrigated conditions, the increased rates of volume and surface area of A-type starch granules were 17.65%-22.88%, 35.8%-39.05%, respectively, in Shannong8355, and 1.56%-5.98%, 2.96%-9.92%, respectively, in Jinan17. Under rainfed conditions, the corresponding rates were 1.46%-2.82%, 7.05%-8.12%, respectively, in Shannong8355, and 1.76%-4.52%, 128%-8.63%, respectively, in Jinan17. On the contrary, either in irrigated or in rainfed cultivation condition, the volume and surface area of B-type starch granules in mature grain had markedly lower percentages than those in mid-filling stage in both cultivars. The alteration of source-sink relation resulted in the noticeable changes of grain starch granule distribution in both cultivation conditions. The percentages of volume and surface area of A-type starch granules were significantly enhanced by the removal of flag leaf and decreased by the removal of half spikelets. As for B-type starch granules, the removal of flag leaf resulted in the decreases in the percentages of volume and surface area, and the significant enhance of the percentages of volume and surface area occurred due to the removal of half spikelets.