The nephrite deposits in China are mainly distributed in Qinghai provinces, among which Yeniugou County is one of the most important nephrite deposits. In this paper, the yellow-green nephrite samples of Yeniugou were tested by conventional gemmology, infrared spectroscopy (FTIR), Raman spectroscopy, electron probe microanalysis (EPMA), and thin section observation, and their mineralogical and spectral characteristics were analyzed. The results show that the refractive index of nephrite in this area is 1.61, the relative density is about 2.97~2.99, the Mohs hardness is 6~6.5, its luster is glass-oil, and the crystallinity is good. The matrix mineral of the sample was tremolite, and the minor minerals were diopside, epidote,sphene, apatite, etc. The contents of oxides in the matrix were w(SiO₂)=58.92%~59.40%, with an average value of 59.19%, w(MgO)=24.70%~25.56%, with an average value of 24.98%, w(CaO)=13.15%~13.43%, with an average value of 13.29%. The particle size of the mineral is about 0.01~1.00 mm. The mineral has a typical felt-like interwoven texture and microscopic dermatoplastic texture, and some micro radial dermatoplastic texture-broom texture can be seen. All mineralogical characteristics are in line with the national identification standard of nephrite.The infrared and Raman spectra of nephrite samples in this area are consistent with the spectral peaks of tremolite. However, the infrared spectral intensity of the sample at 468 cm^-1 is higher than that at 509 cm^-1, and certain peaks in both the infrared and Raman spectra display red or blue shifts. Combined with the chemical composition analysis, it is considered that the tremolite in nephrite is calcareous hornblende, and the shift of spectral peak is related to the Fe, Mn elements or crystal structure. Based on mineralogical characteristics, electron probe test, and field investigation, it is concluded that the nephrite ore body in Yeniugou was formed under the joint action of magnesian marble, basic diabase, and late intermediate-acid magmatic hydrothermalism. Meanwhile, shearing played an important role in the quality of nephrite. In this study, the mineralogical and spectral characteristics of the Yeniugou mining area in Qinghai were determined, and its metallogenic environment was also discussed, which provided a basis for prospecting and deep metallogenic prediction in this area.