Abstract: Comparing with conventional Zr-cladding, SiC composite cladding is expected to slow down accident progression and provide wider margin of coping time by virtue of better radiation resistance, retention of higher strength up to very high temperatures and better oxidation resistance. Under large break loss of coolant accident (LB LOCA), the recession of SiC composite cladding would continue due to the passive oxidation of SiC with low-pressure and high-temperature steam, which consists of two phases: The parabolic oxidation of SiC and subsequent linear volatilization of silica formed on the surface of SiC. In present paper, the modified Deal-Grove model and heat/mass transfer analogy method were utilized to study the SiC parabolic oxidation and SiO₂ linear volatilization rate on the basis of SiC oxidation and SiO₂ volatilization experimental data under pure steam conditions, respectively. Obtained theoretical model shows that under post-LB LOCA low-pressure and high-temperature pure steam oxidation condition, the oxidation rate of SiC is significantly slower than that of Zr (2-3 orders of magnitudes), which results in much less material recession rate of SiC than that of zirconium.