In the rolling process of thick plates， it is easy to have problems of uneven distribution of material structure and coarse grains due to improper process control. In this paper， ultrasonic testing signal on the internal structure of TC4 rolled plate is studied. The results show that the sound attenuation distribution is uniform when the sound wave is incident perpendicular to the plate streamline direction. However， the distribution of sound attenuation is very uneven and stripped in stripe shapes when the incident wave is parallel. For this reason， the section structure with different acoustic attenuation is analyze. It is found that the ultrasonic attenuation is related to the distribution and morphology of α phase in the material：in the area where the sound attenuation is reduced， there are more equiaxed α phases in the material， and the grains are fine and evenly distributed； in the area with large acoustic attenuation， α phase is obviously elongated， the tissue distribution is not uniform， and there is stripe structure.