The starch-based composite materials were prepared by extrusion foaming method with corn starch as the main materials, plasticizer and foaming agent as the additives. The capillary rheometer was used to research the influence of glycerol plasticizer content and NaHCO3 foaming agent content on the rheological behavior of composite foaming material. Scanning electron microscopy(SEM) was also used to observe the effect of different melt viscosity on the cell morphology. The results showed that the melt flow characteristic of starch-based composite foaming material was pseudoplastic. With the increase of glycerol content, the melt viscosity decreased. With the increase of NaHCO3 content, the melt viscosity first decreased and then increased. As the melt viscosity decreased, the number of cell decreased and the pore size increased. When the melt viscosity was 1 200 Pa·s, the cell size was moderate with uniform distribution.