Abstract: In recent years, a kind of high density colourless synthetic cubic zirconia (CZ) has appeared in Wuzhou, Guangxi.But the gemmological characteristics of this artificial gemstone are rarely studied. The gemmological characteristics of this high density CZ were systematically investigated by using Fourier infrared spectrometer, X-ray powder diffractometer, X-ray fluorescence spectrometer and LA-ICP-MS. The results show that the relative density of this high density CZ is about 6.60, and it shows strong blue fluorescence under long and short wavelength ultraviolet light. The density of common CZ is about 5.96, the fluorescence is inert, besides, other conventional gemmological parameters between high density CZ and common density CZ are almost the same. High density CZ contains about 32 wt% Gd element, which is determined to be Gd₂O₃ as a stabilizer. It is speculated that the relative atomic mass of Gd element is high, which leads to a high density of CZ. The molecular formula was calculated based on the LA-ICP-MS data, the relative density of the high density CZ should be 6.93, which is not consistent with the measured value. It can be inferred that the relative atomic mass of Gd element is not the only factor affecting its density. Since the ionic radius of Gd³⁺ is larger than Y³⁺ and Zr⁴⁺, it is speculated that the larger radius of Gd³⁺ will lead to the change of crystal constant, resulting in a slight decrease in density. For the finished product, high density CZ is close to the colour of natural diamond cape series.