Abstract: This article deals with the study on the structure of the granular pearl and the pearl layer developed by stimulating the shells of Pinctada maxima, Pinctada martensi of marine species and Hyriopsis cumingii, Cristaria plicata and Anodonta woodiana of fresh water species. A comparison between these two kinds of powder was made.Pearl and pearl layer in grinding plate were found to be nacreous in structure. The pearl powder was also of nacreous structure, but mixed with some black, yellow and orange particles. The powder of pearl layer was shown to be nacreous in structure mingled with tracular structure occasionally. The powder of the prisms may be of prismatic structure, crossed-lamellar or paraiiei lamellar-structures. Talcum powder is a kind of crystalline of non-structure type. The powder of marine pearl and pearl layer sunk slowly with many floats when put in water, but that of fresh water sunk rapidly with only a few floats.