Three dimensional carbon fiber reinforced silicon oxycarbide (3D Cf/Si-O-C) composites with low cost silicon resin as precursors and 3D Cf as reinforcement. Effects of adding SiC powder (SiCP) on the microstructure, mechanical properties and anti-oxidation properties of 3D Cf/Si-O-C composites were investigated. The results showed that adding SiCP filler could reduce the porosity and improve the interface bonding, therefore the properties of composites increased. But when the SiCP content was excessive, it was difficult to dense the matrix of composites at the further cycles and pores existed in the matrix. As a result, the mechanical properties of the composites decreased. It was found that when fabricated with 18.2 weight percent SiCP the composites exhibited highest mechanical properties, and the flexural strength and fracture toughness reached 421.3MPa and 13.0 MPa•m1/2, respectively. And the anti-oxidation properties were improved with the increase of the SiCP content. When fabricated with 25.0 weight percent SiCP the composites exhibited best oxidation resistance properties, and the composites retained 89.5% of original flexural strength.