This article reviews the related documents about CO2 emission of import and export trade , and deduces and improves the input-output model to eliminate foreign influence of CO2 emission from import product in intermediate investment.. By means of two-pole decomposition method, structural decomposition analysis is conducted on changes of CO2 emission from 1997 to 2007. It has been revealed that improvement of efficiency effect contributes to CO2 emission reduction; reduction effect of productive structure and export structure in corporation has not yet been played, and scale effect increases CO2 emission. At last, the policy based on in-depth calculation on carbon emission of industry sectors has been proposed.