Abstract: A novel structure of double substrates is put forward for a microwave plasma chemical vapor deposition equipment which is used to grow single crystal diamond. Optical Emission Spectrometer (OES) is used to diagnose the intensity of the groups in the plasma, while Raman Spectra and Scanning Electron Microscopy are used to analyze Raman displacement and surface appearance of the single crystal diamond. The effects of the double substrates on OES of the plasma and the growth of single crystal diamond have been studied. The results show that the plasma power density can be enhanced with double substrates. The intensity of OES can be improved with double substrates and resulting in a higher growth rate of single crystal diamond at the same diamond deposition parameters. The single crystal diamond deposited has characteristic of less Raman displacement, smaller full width at half maximum of Raman spectrum and less impurity phases.