Abstract: To address the challenge of handling the thermal boundary conditions in thermal response process of phenolic resin impregnated quartz fiber composites (PISF), a three-dimensional fluid-heat-ablation multi-field coupled model was established. The transient temperature distribution of the material during heating and heat dissipation under high-temperature environment was predicted, and the volume and surface ablation processes were simulated. The influence of various parameters on the heat transfer process of PISF was analyzed. The results indicate that with the increase of time, the surface temperature of the material gradually increases, and the heat flux entering the model decreases. The center point of the heated surface experiences the maximum heat flux and exhibits the most significant ablation. Ablation begins at about 3.6 s. After the material surface being heated, it rapidly decomposes, leading to a peak in gas production rate. Subsequently, due to the surface thermal resistance effect, the gas production rate gradually decreases. Under certain conditions, increasing the thermal conductivity will reduce the ablation regression rate and increase gas production rate, resulting in a higher back temperature, which is unfavorable to thermal insulation of the material. Increasing the specific heat will reduce the ablation regression rate and gas production rate, resulting in a lower back temperature, which is beneficial to thermal insulation of the material. Significantly increasing the permeability will enhance fluid flow heat transfer, increase the ablation regression rate and gas generation rate, resulting in a higher back temperature, which is unfavorable to thermal insulation of the material. The research results contribute to a better understanding of the pyrolysis thermal response process of PISF and provide reference for the optimization design of thermal protection materials.