In order to enhance the ablative resistance of epoxy silicone resin, the ammonium polyphosphate (APP) modified epoxy silicone resin composites were prepared, and the impacts of APP content on the ablative resistance of the composites in an oxygen-acetylene ablation environment were investigated. The results show that the addition of APP can effectively enhance the high-temperature ablative resistance of epoxy silicone resin composites, improving the adhesion strength and integrity of the ablative product layer. When the APP content is 15% , the density and integrity of the ablative product layer formed on the composite are optimal. The linear ablation rate and mass ablation rate are both at their lowest, measuring 0.162 mm/s and 0.065 g/s, respectively, representing a reduction of approximately 44.9% and 75.9% compared to epoxy silicone resin. When the APP content exceeds 15%, there is an increasing tendency for cracking and peeling of the ablative product in the specimens. The addition of APP can reduce the thermogravimetric rate of epoxy silicone resin, and when the addition amount of APP is 15%, the thermogravimetric rate of the composite material is about 32.79%, which is about 43.91% lower than that of epoxy silicone resin.