Diamond crystals were synthesized in FeNiCo-C system with CH4N2S additive at pressure of 6.5 GPa and temperature ranging from 1 300 ℃ to 1 350 ℃, using temperature gradient (TGM) method. The obtained diamond crystals displays yellow color and exhibits cub-octahedral morphology. The surface morphology was characterized by SEM and the results indicate that the surface of the obtained diamond become rougher and rougher with the increasing of CH4N2S addition content in the synthesis system. Furthermore, the Nitrogen (N) and Hydrogen (H) defects and chemical bond structures were analyzed in detail with the help of FT-IR spectra. FT-IR results display that H element exits in the forms of -CH3, -CH2-, C-H and N defects locate in the forms of C, A centers. Additionally, the band locating at 3 300-3 600 cm-1 was observed, attributing to NH absorption.