The invention discloses a preparation method of a buffer material, belonging to the technical field of functional materials. The preparation method comprises the following steps: carrying out steam explosion and sieving on bagasse, so as to obtain primarily processed bagasse; mixing 20-30 parts of the primarily processed bagasse, 3-5 parts of biogas slurry, 3-5 parts of a glucose solution and 30-40 parts of water for fermentation (in parts by weight), filtering, drying, and carrying out ultraviolet light aging, so as to obtain secondarily processed bagasse; mixing and stirring the secondarilyprocessed bagasse with ethyl orthosilicate in a mass ratio of (1 to 10)-(1 to 20), filtering, freezing, crushing, and sieving, so as to obtain modified bagasse; carrying out internal mixing on polylactic acid, adding the modified bagasse, a foaming agent, a plasticizer, a modified filler, calcium hydrogen carbonate, zinc stearate, sodium hydroxide, a coupling agent, phospholipid and a sulfurizingagent, carrying out mixing, calendering formation and sulfuration, and discharging, so as to obtain the buffer material. The buffer material prepared by virtue of the technical scheme has the characteristic of excellent buffer performance and has wide prospects in the development of the technological industry of functional materials.