Abstract: A new theory for choosing the materials was put forward for the first time based on matching factors, providing a theory for choosing the materials in the process of structure designing in aeronautics and astronautics. The importance of materials choosing and material matching in the structure designing was recommended in brief. The general method of materials selected at present was recited, and the limitation of this method was indicated. The guiding principle of the matching calculating method and the standard establishment of matching formulation were put forward. The performance parameters of optical reflector material in common use of space remote sensing camera and structure material were analyzed. The weight coefficient was assigned according to the Delphi method and the hierarchical method, then the matching factor was computed depend on different weight coefficents. The material selected by the matching factor method is the same with a running space remote sensing camera. The results indicate the correctness of selection and the feasibility of the matching calculation.