The invention discloses a root growing and high-yield cultivating method of sweet potato seedlings. The method comprises the following steps of during root growing, cutting 18-25cm of sweet potato seedling in a sweet potato seedling bed, bundling, packaging, soaking 1-2cm of seedling root in a wet environment, maintaining the environment temperature at 25-40 DEG C, growing new roots after 2-3 days, and then transplanting to the field; during cultivating, after conventional cultivating, manufacturing a groove with 3-5cm depth at the edge of a sweet potato cavity, bending the upper part of the sweet potato seedling into the groove, covering the soil on the groove, exposing the head of the sweet potato seedling during soil covering, and fully watering at the upper part. The sweet potato seedling bred by the root growing method has the advantage that after second breeding, the survival rate of sweet potato seedling during cultivating can reach 99%, various types of cultivating are met, and the sweet potato vine in the edge groove can generate the root system again; as the sweet potato seedling is close to the soil surface, the light intensity is sufficient, the growth of root and stem is strong, is well developed, and expands to the deeper layer, the fruiting time of sweet potato is early, the sweet potato is large, and the yield is improved by more than 30% than the yield of traditional direct inserting method.