This work employed an inductively coupled plasma wind tunnel to study the dynamic oxidation mechanisms of carbon fiber reinforced SiC matrix composite (C_f/SiC) in high-enthalpy and high-speed plasmas. The results highlighted a transition of passive/active oxidations of SiC at 800-1600 ℃ and 1-5 kPa. Specially, the active oxidation led to the corrosion of the SiC coating and interruption of the SiO₂ growth. The transition borders of active/passive oxidations were thus defined with respect to oxidation temperature and partial pressure of atomic O in the high-enthalpy and high-speed plasmas. In the transition and passive domains, the SiC dissipation was negligible. By multiple dynamic oxidations of C_f/SiC in the domains, the SiO₂ thickness was not monotonously increased due to the competing mechanisms of passive oxidation of SiC and dissipation of SiO₂. In addition, the mechanical properties of the SiC coating/matrix and the C_f/SiC were maintained after long-term dynamic oxidations, which suggested an excellent thermal stability of C_f/SiC serving in thermal protection systems (TPSs) of reusable hypersonic vehicles.