In order to fabricate high perform carbon fiber reinforced silicon carbide matrix composite (C/SiC). SiC interphase of three dimensional(3D) braided carbon fiber performs was prepared by polymer infiltration pyrolysis(PIP) using polycarbosilane(PCS) as precursor. Then, C/SiC composites were fabricated by gas silicon infiltration(GSI) at 1400～1700°C to C/C greenbody, which was prepared by PIP based on precursor of phenolic resin from one to four cycles. The influence of pyrocarbon(PyC) content in C/C greenbody on the composition, microstructure and mechanical properties of C/SiC composites was investigated via X-ray diffraction(XRD), scanning electron microscope (SEM), physical and chemical methods. The results indicate that there were β-SiC, residual Si ,C and closed pores in C/SiC, and the different pyrocarbon(PyC) content influenced C/SiC mechanical properties via the variable content of β-SiC, residual Si, C and closed pores. The C/SiC composites with 2 cycles of PIP-C, which had fitting relative content of β-SiC, residual Si and C, possessed the best mechanical properties. The flexure strength and flexure modulus were 187.3MPa and 66.5GPa. The β-SiC generated from PCS wrapped the carbon fiber bundles, protecting them from reacting with gaseous silicon. The phenomenon of ‘fibers pull-out’ was observed in all four groups of C/SiC composites, which manifested the mechanism of toughness fracture.