Abstract: The Peristernia reincarnata's exoskeleton being vivid pink appearance, becomes increasingly popular in the market, and its market value is already higher than that of similar organic gemstones (tridacna, Bull's-mouth Helmet，etc). In this papers, the gemmological microscope, XRD spectrometer, Raman spectrometer, FTIR spectrometer equipped with infrared microscope and LIBS were used to study the chemical compositions, structural characteristics and gemmological characteristics of Peristernia reincarnata's exoskeleton. The results indicated that the main chemical compositions of Peristernia reincarnata's exoskeleton is aragonite.In different colour layers, the quantities of trace elements are similar. Therefore, the colour cause of Peristernia reincarnata's exoskeleton may be related to different kinds of organic compounds and its content. According to the semi-quantitative calculations of micro-infrared spectra, the relative content of organic compounds is higher in the pink area, and those of orange and yellow areas are second, and that of the white area is lowest. Based on other test data, the authors speculated that the different colours of Peristernia reincarnata's exoskeleton are related to the different organic compounds. Metalloporphyrin can generate orange and yellow tones, and carotenoids are the reason for pink tones of Peristernia reincarnata's exoskeleton.