With the rapid development of materials science, composite materials and polymer materials are applied in the aerospace area extensively. Nevertheless, existing mature methods of detection can not be used effectively due to the special nature of these materials. But many non-polar, non-metallic materials are transparent for terahertz wave, of which the internal defects can be effectively detected. In this paper, the properties of terahertz and the principles of terahertz nondestructive detection are briefly introduced. Several kinds of composite material widely used in the aerospace field are taken as examples for terahertz nondestructive testing applications.