In order to improve the oxidation resistance of SiC/SiC composites, four types of modified SiC/SiC composites were fabricated by PIP method using polyborosilazane and/or polycarbosilane precursor. The order to use polyborosilazane and polycarbosilane precursor during PIP process plays a key role to affect the oxidation resistance of composites. The SiC/SiBCN-SiC composites reveals the highest oxidation resistance. The SiC matrix outside the SiBCN matrix can effectively inhibit the volatilization of liquid B₂O₃ at 1200 °C. Liquid B₂O₃ filled the micro-cracks of matrix during the oxidation process, which prevent further oxidation damages. Micro-cracks in the matrix of SiC/SiBCN and SiC/SiC-SiBCN composites cannot be sealed due to the volatilization of liquid B₂O₃ at 1200 °C, leading to higher oxidation damages in the composites.