Abstract: In this paper the morphology and quality of diamond films selectively deposited by microwave plasma chemical vapor deposition (MPCVD) on SiO₂ patterned Si substrates were investigated by scanning electron microscope (SEM) and Raman Spectrum. Results indicates that the diamond nucleation density on the SiO₂ mask increases with the substrate temperature,so as to deteriorate the effect of selective deposition of diamond films. This change trend and the optimized deposition temperature were also discussed.