Abstract: Jadeite is well popular by its gorgeous colour and delicate structure. In recent years, due to the shortage of natural jadeite resource, the researches of synthetic jadeite have attracted more and more attention. In this paper, the authors discussed the effect of holding time of synthesis on the quality of jadeite under high pressure and high temperature. The synthetic raw materials were prepared by sol-gel method and they were transformed into jadeite crystal during 1 100-1 500 ℃ under 4.0-6.0 GPa for 1 to 10 hours. The basic gemmological characteristics, infrared spectra and ultraviolet-visible spectra of the synthetic jadeite samples are almost the same as those of natural jadeite. XRD analysis showed that the crystalline purity of jadeite was higher with the increase of synthesis time, and the longer the holding time period was, the sharper the diffraction peak was. SEM and microscopic observation showed that the longer the holding time period was, the better the crystal growth of jadeite, the more compact the structure of jadeite was, and the better the crystal quality of jadeite was.