Abstract: There inevitably exist defects such as pores, microcracks and delamination in C/SiC composites during CVI deposition, resulting in material anisotropy, great acoustic attenuation, and extremely non-uniform microstructure. Therefore, there is hardly any secondary bottom wave appearing during the ultrasound echo test for this material, and the sound velocity cannot be measured by the conventional multiple bottom wave method. This paper proposes a method to measure the sound velocity by using the correlation principle in signal processing, and simulates it with MATLAB to verify the feasibility of the method. The experimental results show that the sound velocity of the six materials is measured by the correlation method, and the error is within 2.5%. Therefore, it is feasible to measure the sound velocity of a C/SiC composite by this method. It has great practical significance for the determination of sound velocity of C/SiC composites.