The foaming effect of the biodegradable buffer material was investigated in this paper. Starch, plant fiber, plasticizer and nucleating agent were mixed, and the mixture was molded. After completion of preparation of materials, the porosity of material was calculated. Porosity reflects the foaming effect of the buffer material. Many factors determine the foaming effect of biodegradable buffer material. The primary and secondary factors were shown: foaming temperature>particle size>foaming time>the ratio of starch and fiber. The porosity of biodegradable buffer material can reach as much as 72.02 percent.