The experiment studied that output of different supplied the potassium level to the sweet potato, and influence of the dry material accumulation and the assignment. The result indicated that, In the certain scope, increasing the potassium level may enhance the output, reduce the photosynthesis potential and improve net assimilation rate, is advantageous to accumulation of dry material; The sufficient supply of potassium, may promote the photosynthesis products to the underground transport raise distribution rate of the dry material and the starch content in the root-tuber, and reduce the starch content in the stem, is advantageous to the material transportation; The sufficient using potash fertilizer, may decrease the protein content in the later period and restrain the activeness of hydro enzyme oxide, so effectively had prevented exuberant growth above the earth, and promotion transform growth center to root-tuber.