The Taguchi method with an L18 orthogonal array design has been used in this study to investigate the effect of various control factors on the performance of microwave plasma enhanced chemical vapor deposition diamond films. The full-width at half-maximum (FWHM) of Raman peak was used as the response item in the design. Raman spectroscopy is one of the most common techniques of diamond film characterization, and in general, the (111) diamond with better crystallinity exhibits a smaller FWHM of the Raman peak (1332 cm(-1)). As the result of Taguchi analysis in this study, the bias voltage, the methane concentration and the hydrogen flow rate are the most influencing factors on the CVD diamond quality. The optimal parameters were also obtained from the Taguchi method. The FWHM in the confirmation experiment is 4.5 cm(-1), while the original 18 runs demonstrate linewidths between 4.7 and 11.6 cm(-1).