Abstract: In view of the insufficient heat resistance and poor ablation resistance of fiber-reinforced phenolic resin composites, island silicate mineral-almandine micropowder (AM) was used as ceramicized filler to modify the boron phenolic resin (BPR), and the molding process was used to prepare different filler contents. AM/BPR ceramizable composite material and high silica glass fiber (HSF)-AM/BPR ceramizable composite material with different filler contents were prepared by molding process. The influence of AM on the heat resistance, ablation resistance and mechanical properties of the boron phenolic resin system, as well as the phase transition and microscopic morphology changes of the material at different temperatures were explored. The results show that as the content of AM increases, the heat resistance of AM/BPR composites increases. A liquid phase is formed above 800℃, and a denser ceramic layer is formed at 1100℃, which is important for the high-temperature performance and ablation resistance of the composite material. When the AM content is 50wt%, the linear ablation rate is 0.221 mm/s, and the mass ablation rate is 0.103 g/s, which is 44.05% and 43.6% lower than that of pure BPR. When the content of AM is 40wt%, the flexural strength of HSF-AM/BPR ceramic composites at room temperature and after high temperature treatment are increased by 29% and 47.97% compared with those without filler, respectively. Its excellent heat resistance, ablation resistance and mechanical properties are expected used as a thermal protection material in the aerospace field.