The invention relates to a 
silicon dioxide hollow sphere / 
polymer composite heat insulating material and a method for preparing the same. The 
composite material comprises a 
polymer substrate and submicron, agglomeration-free and monodisperse 
silicon dioxide hollow spheres evenly dispersed in the substrate, wherein the 
polymer substrate is a substrate of 
epoxy, 
polyurethane or 
polyethylene terephthalate; and for the submicron 
silicon dioxide hollow spheres, the hollow internal 
diameter is between 100 and 720nm, the thickness of the outer wall is between 50 and 100nm, and the weight of the submicron 
silicon dioxide hollow spheres is 1 to 35 percent of that of the 
polymer substrate. In the method, 
powder of the submicron, agglomeration-free and monodisperse 
silicon dioxide hollow sphere is prepared first; the 
powder is modified by the surface modifying technology; and finally, the modified 
powder is combined with the polymer taken as the substrate. The composite heat insulating material shows excellent heat insulating property, and the heat insulating property shows size-dependent characteristics in a rang of submicron. Moreover, because an organic 
foaming agent is not used in the preparation process, the composite heat insulating material is environment-friendly.