The invention discloses a full-degradation cushion packaging material which is prepared from, by weight, 50 parts to 60 parts of starch, 20 parts to 30 parts of plant fibers, 5 parts to 10 parts of packing, 10 parts of 15 parts of starch plasticizer A, 5 parts to 10 parts of starch plasticizer B, 1 part to 5 parts of adhesive, 0.1 part to 1 part of release agent, 0.1 part to 1 part of foaming agent, and 100 parts to 120 parts of water, wherein the plant fibers are straw fibers or bagasse fibers, the packing is talcum powder, the starch plasticizer A is glycerinum or formamide, the starch plasticizer B is urea or ethanediol, the adhesive is polyvinyl alcohol, and the release agent is stearic acid. The invention further discloses a preparing method of the cushion packaging material which is a foaming hot-press forming method. The full-degradation cushion packaging material prepared with the method has the advantages that the raw materials are reproducible, the production process is free of pollution, and production cost is low.