Abstract: Coloured diamonds play an increasingly important role in the jewelry family in recent years.In order to have a better understanding of pricing factors,criteria of rating and evaluation of coloured diamonds,the authors collected and analyzed the auction information of coloured diamonds from Sotheby and Christie in the last 10 years.Research results show that the prices of coloured diamonds are mainly based on the rarity and the consumer's preference of colour.And colour group,saturation,brightness as well as sub-group of colour also influence the prices greatly.Price per carat of coloured diamonds usually is in a direct ratio to their carat weights.Clarity,auction time,sources or brands,diamond type also affect the transaction prices.Although synthetic and improved coloured diamonds may affect the prices sometimes,no direct connections are found between their prices and the natural ones.Besides,it seems that superior coloured diamonds have changed from luxury goods to assets and investments during the financial crisis.In conclusion,colour is the most important pricing factor of coloured diamonds.Therefore we can refer to the coloured diamonds' grading system of GIA and the pink diamonds' grading system of Rio Tinto Group when establishing the coloured diamonds' grading standard suitable for Chinese market.