As a raw material of bioenergy and starch prcessing, the starch content of sweet potato determines the fuel alcohol transform rate and the benefit of prcessing. There is an important route for enhancing the transform rate and the benefit of prcessing of sweet potato by advancing the starch content and breeding high starch high yield varieties. The experiment with different varieties of sweet potato, plus control of fertilizer (N: K_2O=1: 2) and take off branches, using L_9 (3~4) orthogonal experiment...