Abstract: Diamond films are deposited on Si substrate with H₂/CH₄/CO₂ as source using microwave plasma chemical vapor deposition method.The effect of microwave power and CO₂ on the growth of diamond films is analyzed.The quality,surface morphology and grain orientation of diamond film are systematically characterized by Raman spectroscopy,scanning electron microscopy(SEM)and X-ray diffraction(XRD).The results show that an appropriate increase of microwave power could promote the diamond grain growth and increase the(100)orientation.It's also shown that adding an appropriate amount of CO₂ could improve the quality and growth rate of diamond films,and maintain surface morphology.However,with the increase of CO₂ content,the diamond surface morphology changes greatly and the quality and growth rate of diamond films increases firstly and then decreases.