Abstract: Social stocks of metallic substance determine the secondary or recoverable resources to a certain extent. Two methods are given for the social stocks to analyze theoretically the variation of social stocks of metallic substance with the assumption that the metal consumption presents linear or quadratic curves. Exemplifying the copper industry in China, the variations of social stocks of copper and its consumption in the period from 1950 to 2007 were analyzed and the results reveal that the social stocks have come into a quicker growth period since year 2000. Proposes the notion of average age of social stocks of metals and its calculating formula, and an analysis is made to the average age (aa) of copper products in social stocks in the period. It is found that aa of copper products in the period decreased gradually since 1988 and basically remained unchanged from 2005 to 2007, i.e. about 7.8 years.