Abstract: The transparence is an important factor in gem evaluation. Through a series of study and analysis, the results show that the texture is the main factor influencing on the transparence of Xiuyu. Secondly, the crystallization water (including constitutional water, interlayer water and absorbed water) makes an impact on the transparence. Thirdly, the impurity, the crack and the colour of Xiuyu have important effect on its transparence.