Abstract: Cr-Al-Si coating was prepared on the surface of SiC coated C/C composites by the plasma spraying method. The phase composition and microstructure of Cr-Al-Si coating were studied by XRD and SEM. The isothermal oxidation test at 1500℃ was carried out in air. The XRD results show that the outer Cr-Al-Si alloy coating consists of Al_3.21Si_0.47, Cr₃Si and Al₂O₃. The thickness of the coating was about 120μm, and no penetrable crack was observed in the cross-sectional SEM morphologies of the coating. The oxidation resistance of the single porous β-SiC coating is poor, which can only protect C/C composites from oxidation for 10 h with a mass loss of 10%. After adding the Cr-Al-Si alloy outer coating, the double-layer Cr-Al-Si and SiC show a better oxidation protective ability and 5.3% mass loss of the coated sample after oxidation for 61h.