Abstract: The paper aims to study the difference of hydrocyanic acid content in different varieties of Cassava. Used silver nitrate titration method, hydrocyanic acid content was measured in different parts(Leaves, Stems, Root(with periderm), Root(remove periderm)) of seven varieties of cassava(SC5、SC7、SC9、SC124、SC205、SC8013、ZM8625).The results show that , the highest content of hydrocyanic acid in seven varieties of cassava leaves is SC9, the lowest is SC8013; and the highest content of hydrogen cyanide in the stems is ZM8625, the lowest is SC9; the highest content of hydrocyanic acid in the root with periderm is SC205, the lowest is SC7; the highest levels of hydrocyanic acid in the root remove periderm is SC205, the lowest is SC9. Hydrocyanic acid content of all the parts of the SC205 are high. Leaves and stems hydrocyanic acid content is greater than the root in the seven varieties of cassava, the content of hydrocyanic acid in the root with periderm was about twice as high as that of the root remove periderm, The content of hydrocyanic acid in the root remove periderm was significantly lower than that in other parts. The conclusion of this study is the main content of hydrocyanic acid in cassava heavily concentrated in leaf, stem and periderm; the leaves of SC8013 can be developed into high-quality vegetable or feed resources; the root tuber of SC9 can be developed into high quality edible or feed resources.