It has been proved that penicillin spray on Ligusticum chuanxiong can contribute to the growth of the plant in the following ways: cutting down the tissue water potential, strengthening the capability of sucking moisture, increasing the contents of chlorophyll and restraining its degradation to facilitate the formation of photosynthetic compounds, enriching the nutrition root and increasing the root-shoot ratio. All these help to keep the stem tuber rot under 5% so as to guarantee higher economic yield of the plant.