Abstract: Heat-shrinkable material for aviation is a new kind of functional polymer material, which has been widely used recently. In this paper, ultrasonic testing was used to characterize the specimens of heat-shrinkable materials with natural defects. Sound velocity and amplitude attenuation of the material were used for flaw characterization in two scales. The defect zone was also dissected and analyzed based on metallography result. The results indicated that the ultrasonic method could effectively characterize the heat-shrinkable material, but its capability in defect detecting was restricted by the thickness, shape and sound attenuation of the material. Besides, the amplitude attenuation for different heat-shrinkable material is quite different. The amplitude attenuation coefficient for the material containing fluorine is the largest, and becomes smaller for the modified olefin material. It is the lowest for the materials with modified elastomer. Moreover, both defects in macro scale and micro scale in the material can be effectively evaluated by the ultrasonic testing.