Nanometer composites are prepared by hot-pressing-sintering method in the paper, using nanometer Si-C-N particles as reinforce phase, Si₃N₄ as matrix phase, the bending strength of the materials reaches 878.5MPa and the fracture toughness reaches to 11.96 MPam^1/2. The hot-pressed samples structure is characterized by scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM) at the same time, the relationship between the structure and the property is discussed.