The invention discloses a silicified diamond/SiC composite material preparation method, which belongs to the field of electronic packaging materials. Diamond particles and silicon powder are firstly subjected to wet mixing, sintering is carried out after thorough grinding, the diamond surface and the silicon powder react, and a layer of silicon carbide coating is generated; then, the diamond particles with the surface coated with the silicon carbide and the silicon powder are mixed, an organic binder is added at the same time, grinding is carried out, mixing on a mixer is carried out, and uniform composite particles are obtained; the composite particles are subjected to prepressing and debinding and are transferred to a vacuum infiltration furnace, a silicon burial method is adopted for vacuum infiltration, and a compact diamond/SiC composite material is prepared. The silicon powder is adopted to modify the diamond particles, the interfacial bonding between diamond and silicon is improved, the compactness of the obtained diamond/SiC composite material is more than 95%, the hardness is above HRA 80, the bending strength exceeds 200 MPa, the thermal conductivity reaches 600 W/mK, andthe thermal expansion coefficient 1.5 to 4*10<-6>/K. Thus, multiple products with complex characters, complex curvature and large size can be prepared at one time, the production efficiency is high,and the cost is low.