The invention discloses a method for preparing an amorphous silicon carbide ceramic-diamond composite coating. The method comprises the steps of cracking macromolecular organic silane serving as a precursor on the surface of a substrate by adopting a macromolecular precursor cracking method to generate an amorphous silicon carbide ceramic film, and then performing in-situ deposition on the micro diamond film by adopting a hot filament chemical vapor deposition method to obtain the amorphous silicon carbide ceramic-diamond composite coating. Compared with the prior art, the amorphous silicon carbide transition layer prepared by adopting the macromolecular precursor cracking method can be used for effectively blocking residual cobalt phase on the surface of a hard alloy matrix after two-step treatment and improving the rough surface of the hard alloy matrix; and the prepared amorphous silicon carbide ceramic-diamond composite coating has excellent adhesion and extremely high abrasion resistance, and is suitable for preparing high-quality diamond coating cutters.