In this paper, a new structure was designed and tested for the substrate holder of crystal diamondEffect of the proposed substrate holder was verified by several experiments. The experiments related to single diamonds were carried out on the traditional and the proposed substrate holders respectively. The experimental results show that the single diamond with the thickness of 1.66 mm is obtained by continually growing of 48 h, and achieved the high quality single diamond of 3 mm by repeating the growth on the proposed substrate holder. The proposed substrate holder can restrain the occurrence of temperature drifting of large grains during the deposited process and provide a suitable environment for diamond homoepitaxial growth. The polycrystalline diamonds around diamond seeds can be suppressed and high purity chemical vapor deposition single diamonds with thickness of larger than 3 mm can be successfully fabricated by the proposed substrate holder and high power density microwave plasma chemical vapor deposition method. seeds to solve the problems of inhomogeneously distributed temperature. A through-hole was drilled on the substrate holder, and the AlN sheets were added to the contacted areas where the diamond epitaxial growth process was carrying out. With such a substrate holder structure, direct contact between diamond seeds and substrate can be avoided, so as to ensure the essentially homogeneous temperature distributions simutaneouslyEffect of the proposed substrate holder was verified by several experiments. The experiments related to single diamonds were carried out on the traditional and the proposed substrate holders respectively. The experimental results show that the single diamond with the thickness of 1.66 mm is obtained by continually growing of 48 h, and achieved the high quality single diamond of 3 mm by repeating the growth on the proposed substrate holder. The proposed substrate holder can restrain the occurrence of temperature drifting of large grains during the deposited process and provide a suitable environment for diamond homoepitaxial growth. The polycrystalline diamonds around diamond seeds can be suppressed and high purity chemical vapor deposition single diamonds with thickness of larger than 3 mm can be successfully fabricated by the proposed substrate holder and high power density microwave plasma chemical vapor deposition method.