Abstract: CVD diamond films have been prepared by MPCVD technology using the mixture gas of CH₄,H₂and Ar at relative low substrate temperature.Scanning electron microscope,X-ray diffraction and Raman spectrum have been used to evaluate the surface morphology,growth structure and quality of the deposited diamond films.The results show that introducing Ar can reduce the substrate temperature effectively for the deposition of CVD diamond film.However,the increase of microwave power is necessary to improve the quality of diamond film.Meanwhile,the diamond films with similar surface morphology can be obtained at CH₄/H₂/Ar and CH₄/H₂,respectively when the substrate temperature is kept constant.And the microwave power used for the deposition of diamond films with CH₄/H₂/Ar maybe lower.