With polyacrylonitrile-based carbon fibers being the reinforcement, carbon aerogels composites (C/CA) with nano-porous carbon aerogels distributing in the carbon fibers matrix were prepared by vacuum impregnating, gelation, aging, supercritical drying and pyrolysis.Then the composites was further coated by silicon oxycarbide (SiCO) aerogels to improve its oxidative-resistant performance.Specifically, the SiCO sol was prepared with methyltrimethoxysilane(MTMS) as silicon source, dimethyldiethoxylsilane (DMDES) as carbon source, ethylalcohol (EtOH) as solvent, HNO3 and NH3·H2O as catalysts by acid-alkaline two-step catalytic method.Then the SiCO sol was impregnated in the C/CA composites.After gelation, aging, solvent exchange, ambient drying and pyrolysis, anti oxidation carbon aerogel composites (C/CA-SiCO) with high temperature resistance and high-performance heat insulation were obtained.The as-prepared composites were characterized with X-ray diffraction (XRD), scanning electron microscopy (SEM), Hot Disk method and infrared spectroscopy (FTIR).From the SEM images, the inner of C/CA is coated with SiCO aerogels.With the times of impregnating increasing from 1 to 3, the density of the composites increases from 0.35 g/cm3 to 0.65 g/cm3 (it is 0.15 g/cm3 for the C/CA), the thermal conductivity of composites increases from 0.53 W/m·K to 0.78 W/m·K (0.14 W/m·K for the C/CA), the weight loss after 1600℃/20min heat treatment in air for four times decreases from 24% to 1.3%.The linear shrinkage of the as-prepared composites is less than 2%.It is found that after oxidation resistance test, the surface of the C/CA-SiCO is full of β-SiO2 crystalline whereas its inner remains amorphous.FTIR shows that the characteristic peaks of composites have no obvious changes after oxidation resistance test.