Three-dimensional silica fibers reinforced nitride matrix composites （3D SiO₂f/Si₃N₄-BN） were prepared through repeated infiltration and pyrolysis. The ablation performance of the composites was evaluated by arc jet. The ablation surface and microstructures were studied by scanning electron microscope (SEM) and Energy dispersive spectroscopy (EDS). The results show that the 3D SiO₂f/Si₃N₄-BN composites have a low linear ablation rate of 0.91mm/s under high pressure and heat flux. Silica fibers fused and more heat was absorbed before the fused layer was swept off and the matrix eroding velocity reduced for the protective melt layer. On the other hand, the fused layer was prevented from eroding from the ablation surface as a result of the matrix with high mechanical property and sublimation temperature. The nitride composite is a high-temperature ablation resistance material for its low recession rate under high thermal load.