In order to enhance the oxidation resistance of C/Si C composites, mullite/yttrium silicate coatings were fabricated on C/Si C composites through dip-coating route. Al_2O_3-SiO_2 sol with high solid content was selected as the raw material for mullite and “silicone resin + Y_2O_3 powder” slurry was used to synthesize yttrium silicate. The microstructure and phase composition of coatings were characterized, and the investigation on oxidation resistance and anti-oxidation mechanism was emphasized. The as-fabricated coatings consisting of SiO_2-rich mullite phase and Y_2Si_2O_7 phase show high density and favorable bonding to C/Si C composites. After oxidized at 1 400 ℃ and 1 500 ℃ for 30 min in static air, the coating-containing C/Si C composites possess 91.9% and 102.4% of the original flexural strength, respectively. The desirable thermal stability of coatings and the further densification of coatings due to viscous flow of rich SiO_2 and Y-Si-Al-O glass are responsible for the excellent oxidation resistance. In addition, the coating-containing composites retain 99.0% of the original flexural strength and the coatings exhibit no cracking and desquamation after 12 times of thermal shock from 1 400 ℃ to room temperature, which are ascribed to the combination of anti-oxidation mechanism and preferable physical and chemical compatibility among C/Si C composites, mullite and Y_2Si_2O_7. The carbothermal reaction at 1 600 ℃ between free carbon in C/Si C substrate and rich SiO_2 in mullite results in severe frothing and desquamation of coatings and obvious degradation in oxidation resistance. In order to enhance the oxidation resistance of C / Si C composites, mullite / yttrium silicate coatings were fabricated on C / Si C composites through dip-coating route. Al 2 O 3 -SiO 2 sol with high solid content was selected as the raw material for mullite and The microstructure and phase composition of coatings were characterized, and the investigation on oxidation resistance and anti-oxidation mechanism was emphasized. The as-fabricated coatings consisting of SiO 2 - rich mullite phase and Y_2Si_2O_7 phase show high density and favorable bonding to C / Si C composites. After oxidized at 1 400 ℃ and 1 500 ℃ for 30 min in static air, the coating-containing C / Si C composites possess 91.9% and 102.4 % of the original flexural strength, respectively. respectively. The desirable thermal stability of coatings and the further densification of coatings due to viscous flow of rich SiO 2 and Y-Si-Al-O glass are responsible for the e In addition, the coating-containing composites retain 99.0% of the original flexural strength and the coating exhibit no cracking and desquamation after 12 times of thermal shock from 1 400 ° C to room temperature, which arecribed to the combination of anti -oxidation mechanism and preferable physical and chemical compatibility among C / Si C composites, mullite and Y_2Si_2O_7. The carbothermal reaction at 1 600 ° C between free carbon in C / Si C substrate and rich SiO_2 in mullite results in severe frothing and desquamation of coatings and obvious degradation in oxidation resistance.