Diamond nitrogen vacancy (NV) color centers have good stability at room temperature, long electron spin coherence time, and can be manipulated by lasers and microwaves, making them the most promising structure in the field of quantum detection. Within a certain range, the higher the concentration of NV color centers, the higher the sensitivity of detecting physical quantities. Therefore, it is necessary to dope sufficient nitrogen atoms into diamond single crystals to form high concentration of NV color centers. In this study, diamond single crystals with different nitrogen content were prepared by microwave plasma chemical vapor deposition (MPCVD) to construct high concentrations of NV color centers. By doping different amounts of nitrogen atoms into the precursor gas, many problems encountered during long-time growth of diamond single crystals under high nitrogen conditions were solved. Diamond single crystals with nitrogen contents of approximately 0.205 ppm, 5 ppm, 8 ppm, 11 ppm, 15 ppm, 36 ppm, and 54 ppm were prepared. As the nitrogen content increased, the width of the step flow on the surface of the diamond single crystal gradually widened, eventually the step flow gradually disappeared and the surface became smooth. Under the experimental conditions of this study, it was preliminarily determined that the average ratio of the nitrogen content in the precursor gas to the nitrogen atoms content introduced into the diamond single crystal lattice was about 11. Fourier transform infrared spectroscopy shows that as the nitrogen content inside the CVD diamond single crystal increases, the density of vacancy defects also increases. Therefore, the color of CVD high nitrogen diamond single crystals ranges from light brown to brownish black. Compared with HPHT diamond single crystals, the intensity of absorption peak at 1130cm<sup>-1</sup> is weaker, absorption peak at 1280cm<sup>-1</sup> was not shown. Three obvious nitrogen related absorption peaks at 1371cm<sup>-1</sup>, 1353cm<sup>-1</sup>, and 1332cm<sup>-1</sup> of CVD diamond single crystal were displayed. Nitrogen atoms mainly exist in the form of aggregated nitrogen and single substitutional N<sup>+</sup> in diamond single crystals, rather than in the form of C-defect. The PL spectra results showed that defects such as vacancies inside the diamond single crystal with nitrogen content of 54 ppm were significantly increased after electron irradiation, leading to a remarkable increase in the concentration of NV color centers. The magnetic detection performance of the NV color center material after irradiation was verified, the fluorescence intensity was uniformly distributed in the sample surface. The diamond single crystal with nitrogen content of 54 ppm had good microwave spin manipulation, its longitudinal relaxation time was about 3.37 ms.
