Abstract: In this paper, C_f/SiC was prepared by the process of precursor-infiltration-pyrolysis(PIP) using carbon fiber bundles and polycarbosilane(PCS), and the damage extent of fibers in C_f/SiC was studied. The results show that strongly bonded fiber/matrix interface will come into being because PCS is ready to pyrolyze surrounding the fibers, and the considerable oxygen and impurity hurts the fiber. At the same time, the thermal stress hurts the fiber greatly, which is caused by the imparity of the fiber-matrix coefficients of thermal expansion and considerable bulk-shrink in the process of pyrolysis.