Abstract: The interphase modified coating plays a vital role in adjusting the mechanical properties of composites, in particular for those C_f/SiC composites prepared from the gaseous silicon infiltration (GSI) process. The ideal interphase modified coating should not only prevent the etching of C fiber by Si vapor, but also render a good interface bonding between C fiber and SiC matrix. With SiC coatings from the precursor infiltration-pyrolysis (PIP) route as the interphase modified coating in 3D-C fiber preform, we discuss the effects of PIP-SiC coating on mechanical properties of C_f/SiC composites made from GSI. The results show that, without coating modification, the GSI C_f/SiC composites have poor mechanical properties and show brittle fracture characteristic, with the flexure strength, flexure modulus and fracture toughness 87.6 MPa, 56.9 GPa and 2.1 MPa·m^1/2, respectively. Those composites with PIP-SiC interphase modified coating exhibit better mechanical properties, with PIP-SiC coating modification, with the increase of the PIP-SiC cycles, flexure strength, flexure modulus and fracture toughness of GSI C_f/SiC composites decrease, in particular those with the PIP-SiC coatings after one cycle, with the flexure strength, flexure modulus and fracture toughness 185.2 MPa, 91.1 GPa and 5.5 MPa·m^1/2, respectively. The improvement effects from the PIP-SiC interphase modified coating are attributed to the transfer loading and prevention of etching by Si.