The invention discloses a preparation method of a biodegradable bactericidal cushion packaging material, belonging to the field of cushion packaging materials. The preparation method comprises the following steps: treating the towel gourd ladle, adding polyase to prepare a cushion packaging material base, mixing the cushion packaging material base with lactic acid, starch, water and sodium ethylate to react, adding saponin and onion juice into the mixture, and immersing to obtain the biodegradable bactericidal cushion packaging material. The cushion material prepared by utilizing the plant fiber structure in the towel gourd ladle has the advantages of light weight, high processability, high biodegradability, favorable cushioning property, abundant raw materials, low cost and environment friendliness. By adding the antimicrobial aid, the cushion packaging material has favorable antimicrobial property, and lowers the survivability of pathogenic bacteria or mold in the plant fiber environment.