Abstract: Carbon/phenolic composites have emerged as key ablation-resistant materials for advanced thermal protection systems in spacecraft re-entry and solid rocket motor nozzles, owing to their unique thermo-structural stability and multiphase conversion behavior under extreme conditions. Their ablation performance is governed by highly coupled processes involving pyrolysis, carbonization, ceramization, gas evolution, solid-phase microstructural evolution, and complex gas-solid-flow interactions. Herein, this article reviews systematically the recent research progress on the pyrolysis behavior and ablation mechanisms of carbon/phenolic composites, especially in material design optimization, pyrolysis kinetics modelling, experimental characterization under aerothermal and gas-solid coupling environments, and multiscale simulation approaches. The current challenges and future perspectives in understanding the multi-physics ablation mechanisms were discussed to provide guidance for the design and engineering application of next-generation high-performance ablative composites.