The invention relates to a fungus-based biomass packaging material with bagasse as a main material and a preparation method of the fungus-based biomass packaging material. The biomass packaging material is prepared from the bagasse, straw filaments and a biomass packaging material additive, wherein the biomass packaging material additive is prepared from the following components in parts by mass: 52 parts of wheat bran, 10 parts of corn meal, 12 parts of soybean meal, 6 parts of soluble starch, 10 parts of quick lime and 10 parts of gypsum powder. The preparation method comprises the getting ready of an incubating material, the pre-incubation of a culture, mold filling and incubation, and the drying of a sample. The preparation method provided by the invention has the advantages of simple production process and low-cost production; the made biomass packaging material is environment-friendly and ecological, has a favorable degradable property and excellent mechanical performance, can be used for effectively reducing environmental pollution, and is an ideal environment-friendly packaging material.