Abstract: In recent ten years，the price of diamonds from 1 ct to 5 ct has been rising，especially the price of 3 ct diamond boomed quickly．It is hard to analyze the mass of data in the Rapaport diamond quotation 1ist．In the paper，the author introduces a new analytical method，which is practical，logical，effective and close to the market．The author analyzes the average price data of diamonds in recent ten years and then offers some information on investment dynamic and buying guide of diamond．