Abstract: Diamond film's nucleation and growth affects the quality of diamond film. This paper researched the nucleation quality of diamond coating on silicon nitride ceramic tools in different technology conditions in a new model stainless steel resonant cavity type microwave plasma CVD equipment which was made by our lab. The plasma ball's diameter is about 76 mm and homogeneous temperature distribution can realize homogeneous growth of diamond film.We examined and analyzed with scanning electron microscopy (SEM), laser Raman spectrometer (Raman) and researched a preparation technology of diamond coating on silicon nitride ceramic tool in high speed growth and high quality.And the cutting performance of the coating tools in the technology conditions was tested. The results showed that average applied lifetime of coating tools improved over 10 times to that of silicon nitride ceramic tools in cutting 18wt; Si-Al alloy.