Abstract: During planetary entry and Earth return missions, spacecraft surfaces experience significant thermal radiation effects due to high-enthalpy, high-velocity gases. Unlike conductive heat transfer, the volumetric radiation effect depends critically on the radiative properties of thermal protection materials. The lightweight needled quartz fiber/phenolic composite, with its high porosity and semi-transparent characteristics, demonstrates particularly favorable radiative heat transfer properties. This study developed an improved thermal response model by incorporating volumetric radiative transfer equations into conventional ablation models. Comparative analyses with experimental data demonstrated that the proposed volumetric radiation-ablation model achieved superior prediction accuracy compared to traditional approaches. The results revealed that composites with higher absorption and scattering coefficients exhibited enhanced thermal insulation performance. Under high-radiation heating conditions, accelerated pyrolysis of phenolic resin occurred within the composite material, accompanied by increased internal pyrolysis gas pressure. Conversely, high convective heating conditions primarily elevated the surface ablation recession rate. These findings provide valuable insights for engineering applications of lightweight needled quartz fiber/phenolic composites in thermal protection systems for deep space exploration vehicles.