The FTIR and Raman spectra of 10 diamonds from Yuanshui, Hunan province show that the alluvial diamonds from this area are mostly IaAB type, with a significant character that the A-center is enriched relatively; the nitrogen concentration in the diamonds is between 38.20 and 840.67 μg·g-1, which has a tremendous distinction in different crystal. The residence time of the diamonds in the mantle are between 0.043 and 3.315 Ga, which is also has a great difference in different diamond grains. The remotest residence time (3.315 Ga) of one diamond is older than the most aged rock (3.285 Ga) in Xiang-E-Qian-Gui contiguous zone. A remarkable environment change had took place during the process of diamonds formation. The formation depth of dodecahedral diamonds is deeper than that of the octahedral ones.