Abstract: In international coloured gemstone trade, all the asking price and bid price are given according to the total quality grade (1 to 10 ) and carat of coloured gemstones. In order to regularize our gem and jewelry appraisal, it is vital important to describe and grade coloured gemstones in scientific way. GemDialogue and GemSet are the two important colour systems, and they are widely used by international jewelry appraisers. In the paper, the two systems are introduced and the application of the two systems in coloured gemstones grading are discussed.