Abstract: By observing the pearl's surface and interior structure, and making statistical analyses of relationship between the pearl's quality(luster, colour, shape, size, etc) and the freshwater mussel's species, size, colour, the health condition and the pearl producing site, the main factors affecting the quality of cultured pearl are the pearl's commponent and structure, the varieties of the freshwater mussels, the growth environment, the culturing technology and so on.