Abstract: To evaluate the contribution of the thermal blocking effect to the heat protection of silicone resin-carbon fiber fabrics composites, a mathematical model of the thermal response process was established based on the ablation and thermal degradation behavior of silicone resin. The temperature of the back side of the silicone resin-carbon fiber fabrics composite and thermo-physical parameters of the silicone resin have been predicted by this model. The analysis of the thermal blocking effect on the thermal performance of silicone resin-carbon fiber fabrics composite was mainly focused on. The results show that when the silicone resin-coated carbon fiber fabrics are ablated under 400 kW/m² heat flow, most of the thermal blocking effect comes from the ejection gas generated by the decomposition of the silicone resin in 40 s, and it completely comes from the ejection generated by carbon combustion after 40 s. The blocking factor reaches the minimum at 10 s, which blocks 121.6 kW/m² heat flow into silicone resin. During the entire ablation process, the thermal blocking effect reduces 4.1% percent of the total heat entering the silicone resin. Among the thermophysical parameters, the thermal blocking effect has the greater influence on the density of the silicone resin than its thermal conductivity and specific heat capacity. Compared with increasing the mass flow rate of the pyrolysis gas of the silicone resin, prolonging the time for the silicone resin to escape the gas can significantly improve the thermal blocking effect and achieve a better heat protection effect.