Abstract: ObjectiveStarch grain structure in root tuber of cassava varieties with different starch contents and its re-lation to starch content were studied, so as to provide theoretical basis for starch storage and breeding of cassava.MethodTaking high-starch cassava varieties GR891,Fuxuan 01 and low-starch cassava variety SC124 as materials, the starch grain structure in root tuber of different cassava varieties were studied by morphology anatomy ,paraffin section and scanning electron microscopy of root tuber. ResultAt seedling stage, starch was mainly stored in secondary xylem. At root tuber formation stage, starch grains were abundant. Most of them were stored at starch storage area and a small amount were distributed at cortex, but starch grain density in starch storage area was higher than that in cortex. In secondary xylem region near the middle column,starch grains were distributed in a radial arrangement. There was no significant difference in morphology of starch grains between different cassava varieties,and most of them were irregular semicircle and elliptical. Starch grain diameter of high-starch varieties was smaller than that of low-starch varieties , but the difference was insignif-icant(P>0.05). ConclusionThe main position of starch accumulation in root tuber of cassava is starch storage area. In catheter interior and adjacent areas, the number of starch grain is large, grain diameter is small, and filling degree is high. Aggregation degree of starch grain in high-starch cassava varieties is higher than that of low-starch cassava varieties at root tuber formation stage.