Since 1993,China has become a net imp ort country of energy.And with China' s high rate of develop-ment,the gap between oil production and oil demand is becoming more and mo re obvious.How to secure the country' s oil supply has aroused a lot of atten tion.Based on the method used by many researchers,this paper offers a quantification method to evaluate the supply diversification of a country and makes some policy recommendations on how to study the question of China' s oil security.