According to the image blur problem caused by scattering photon which was received by detector in the CT detection progress of C/C composites， a mathematical model was established which described the physical processes such as absorption and scattering of photon. The mathematical model was solved by Monte Carlo method. Based on these， this work proposed a scatter correction method with photon transport and conducts comparison analysis on different size of C/C composites. The research indicates that the mathematical model built in this paper can describe the physical processes such as absorption and scattering of photons exactly， the proposed method could effectively suppress the scattering photons and improve the image quality. With the growing size of C/C composites， the effect of scattering photon on the image quality is greater. As the decreasing size of C/C composites， the greater scatter correction and high sensitive obtained. The method in this paper can effectively improve the density resolution of images and the detection ability of C/C composite defects.