NOVELTY - Biological liquid comprises (in parts weight): light rare earth element (10-30), amino acid (30-55), soil sterilizing agent (2-5), soil disinfecting agent (2-5), disease resisting medicine (5-15), boric acid (0.5-2), zinc sulfate (1.5-3), sodium benzoate (0.5-2) and water (10-20).    USE - The biological liquid is useful for preventing ginger (Zingiber officinale roscoe) bacterial wilt (claimed).    ADVANTAGE - The biological liquid prevents secondary pollution caused by chemical, is environmentally-friendly and can be prepared by simple method.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for method of preparing the biological liquid, which involves (a) detecting tissue of raw material, dissolving the raw materials in water and regulating stable pH value, (b) placing the obtained solution of fixed volume in reaction pot having calibration for measuring weight of the solution to 500 kg, (c) adding the light rare earth element into a ceramic or stainless steel container in batch, regulating the pH to 3-4 using tapping water or well water at room temperature, slowly agitating the container for 2-3 hours and dissolving the rare earth elements, (d) adding zinc nitrate into water at 7-8 degrees C and regulating pH to 4-5 using glacial acetic acid and dissolving zinc nitrate, (e) selecting two or three auxiliary materials from amino acid, soil sterilizing agent, soil disinfecting agent and disease resisting medicine and mixing the selected materials uniformly by agitating, (f) adding the amino acid, soil sterilizing agent and soil disinfecting agent into the reaction pot, and rare earth element into the reaction pot, adding disease resisting medicine into the reaction pot, adding boric acid into the reaction pot and agitating the raw material in the reaction pot, (g) adding sodium benzoate and immersed zinc sulfate into the reaction pot containing raw materials of step (f) and continually agitating for 5-6 hours, and (h) agitating and regulating the pH of the liquid in the reaction pot, dissolving the liquid in the reaction pot, opening the valve of the reaction pot and transferring the liquid from the reaction pot into a storing pot and regulating the pH.