During the process of preparing the biomass foam materials with starch and EVA as raw materials, the process parameters have great influence on the preparation of foam composite materials. The effects of screw speed on plasticizing morphology, feeding rate on preparation process, extrusion die orifice temperature on bubble size and material moisture content on expansion rate were focused in research. The study showed that when the screw rotation speed was set at 120 r/min, the plasticizing effect of Starch/EVA composites extrusion foaming was optimal. Feeding speed would affect the whole extrusion process. By adjusting the feeding speed, the“bridge”“blocked”phenomena could be avoided. When the die temperature was set to 160 ℃, with the complete resolving of foaming agent, the bubble could reach the complete maximization. Moisture content had a great influence on starch /EVA composite foaming material. When moisture content rate in raw materials was 14%, the swelling rate reached the maximum value of 14.4%.