Abstract: In field conditions, Using two cassava cultivars SC124 and FuXuan01 as the materials, determine root’s starch accumulation and root,stem,leaf soluble sugar accumulation in the growth period respectively,study the relationship between cassava soluble sugar’s transportion, distribution and the root’s starch accumulation.The results showed that root’s soluble sugar content was significantly decline tendency from the root formation in the early period to mature period, and stem and leaf’s soluble sugar content first with root starch accumulation rate rise, then with the starch accumulation rate decline always significantly higher, keep the opposite trend with starch accumulation rate. In the early root formation, the distribution of soluble sugar is that root accumulation is greater than the stem, stem is greater than the leaf,but in the mature period, root soluble sugar accumulation less than the stem, the stem less than the leaf. Thus it can be seen,the relationship between soluble sugar's transportion,distribution and the root’starch accumulation in cassava is very close,and the main factor of limiting root starch accumulation is library limit. Besides, the high starch varieties have stronger the ability to synthesis assimilate soluble sugar.