Mineralogical, gemological and spectral characteristics and chemical constituents of all kinds of green Manasi nephrite were studied by using slice observation, electron microprobe analysis and infrared spectra. The results indicate that the main mineral components are tremolite and actinolite and that the emerald green spotted structure "Cuihua" of Manasi green jade is formed from early actinolite. The material composition features indicate that green Manasi nephrite is a product of the alteration of ultrabasic rock.